---
title: "Wedge-Lock Washer Pairs"
description: "Wedge-Lock Washer Pairs to Trade series (cam wedge-lock pair): sizes M6 to M20, id 6.4-21.4 mm, od 10.8-30.7 mm. Technical drawing redraws to any row."
url: https://engineeringhardware.com/fastener/wedge-lock-washer-pairs/
source: Engineering Hardware & Fasteners
---

# Wedge-Lock Washer Pairs

Washers · Wedge-Lock Washers

6 catalogued sizes, dimensioned to Trade series (cam wedge-lock pair). Pick any row and the technical drawing redraws to it.

Wedge-Lock Washer Pairs to Trade series (cam wedge-lock pair) are catalogued in sizes M6 to M20, with id 6.4-21.4 mm, od 10.8-30.7 mm, thick 2.5-5.2 mm. 6 sizes are held in the table below, and the technical drawing redraws to whichever row you select.

- **Standard:** Trade series (cam wedge-lock pair)
- **Size range:** M6-M20
- **ID:** 6.4-21.4 mm
- **OD:** 10.8-30.7 mm
- **Catalogued sizes:** 6

Dimensions are nominal values from the governing standard. Confirm the tolerance class for your application before ordering.

![Wedge-Lock Washer Pairs technical product image](https://engineeringhardware.com/wp-content/uploads/2026/09/Wedge-Lock-Washers.webp)

Product catalog

## Related Wedge-Lock Washers products

[![304 Stainless Steel Zinc Plated EPDM Rubber Sealing Washers Composite Waterproof Gaskets Non-Slip Compound Washer M4.2-M12](https://img.engineeringhardware.com/304-Stainless-Steel-Zinc-Plated-EPDM-Rubber-Sealing-Washers-Composite-Waterproof-Gaskets-Non-Slip-Compound-Washer-M4-2-M12.webp)](https://engineeringhardware.com/product/304-stainless-steel-zinc-plated-epdm-rubber-sealing-washers-composite-waterproof/)

Wedge-Lock & Anti-Vibration Washers

### [304 Stainless Steel Zinc Plated EPDM Rubber Sealing Washers Composite Waterproof Gaskets Non-Slip Compound Washer M4.2-M12](https://engineeringhardware.com/product/304-stainless-steel-zinc-plated-epdm-rubber-sealing-washers-composite-waterproof/)

Wedge Lock Washer · Stainless Steel / Carbon Steel

**US$0.036 – 0.36**MOQ 1,000 pieces

[![Anti-Vibration DIN25201 Finish Zinc Plated Stainless Double Fold Self Locking Round Washer](https://img.engineeringhardware.com/Anti-Vibration-DIN25201-Finish-Zinc-Plated-Stainless-Double-Fold-Self-Locking-Round-Washer.webp)](https://engineeringhardware.com/product/anti-vibration-din25201-finish-zinc-plated-stainless-double-fold-self-locking-round/)

Wedge-Lock & Anti-Vibration Washers

### [Anti-Vibration DIN25201 Finish Zinc Plated Stainless Double Fold Self Locking Round Washer](https://engineeringhardware.com/product/anti-vibration-din25201-finish-zinc-plated-stainless-double-fold-self-locking-round/)

Lock Washer · Carbon Steel

**US$0.012 – 0.036**MOQ 500 sets

[![Lock Preventing Double Fold Self Wedge Lock Washer Nl6 S6oc Carbon Steel Stainless Steel and Steelplain DIN Light Industry](https://img.engineeringhardware.com/Lock-Preventing-Double-Fold-Self-Wedge-Lock-Washer-Nl6-S6oc-Carbon-Steel-Stainless-Steel-and-Steelplain-DIN-Light-Industry.webp)](https://engineeringhardware.com/product/lock-preventing-double-fold-self-wedge-lock-washer-nl6-s6oc-carbon-steel-stainless/)

Wedge-Lock & Anti-Vibration Washers

### [Lock Preventing Double Fold Self Wedge Lock Washer Nl6 S6oc Carbon Steel Stainless Steel and Steelplain DIN Light Industry](https://engineeringhardware.com/product/lock-preventing-double-fold-self-wedge-lock-washer-nl6-s6oc-carbon-steel-stainless/)

Lock Preventing Washers · DIN

**US$0.24**MOQ 100 pieces

[![Stainless Steel Self Locking Washer M3m5m8 Wedge Lock Custom Lock Washer DIN25201](https://img.engineeringhardware.com/Stainless-Steel-Self-Locking-Washer-M3m5m8-Wedge-Lock-Custom-Lock-Washer-DIN25201.webp)](https://engineeringhardware.com/product/stainless-steel-self-locking-washer-m3m5m8-wedge-lock-custom-lock-washer-din25201/)

Wedge-Lock & Anti-Vibration Washers

### [Stainless Steel Self Locking Washer M3m5m8 Wedge Lock Custom Lock Washer DIN25201](https://engineeringhardware.com/product/stainless-steel-self-locking-washer-m3m5m8-wedge-lock-custom-lock-washer-din25201/)

Customized · Stainless Steel

**US$0.0012 – 0.03**MOQ 1,000 pieces

[![Stainless Steel 316/304 DIN25201 Polished Wedge Lock Washer Self Locking High Strength Anti Vibration Full Range in Stock](https://img.engineeringhardware.com/Stainless-Steel-316-304-DIN25201-Polished-Wedge-Lock-Washer-Self-Locking-High-Strength-Anti-Vibration-Full-Range-in-Stock.webp)](https://engineeringhardware.com/product/stainless-steel-316-304-din25201-polished-wedge-lock-washer-self-locking-high/)

Wedge-Lock & Anti-Vibration Washers

### [Stainless Steel 316/304 DIN25201 Polished Wedge Lock Washer Self Locking High Strength Anti Vibration Full Range in Stock](https://engineeringhardware.com/product/stainless-steel-316-304-din25201-polished-wedge-lock-washer-self-locking-high/)

Lock Washer · Stainless Steel

**US$0.012 – 0.036**MOQ 500 sets

[![OEM Black Nylon Insulating Flat Plastic Spacer Anti Vibration Silicone Rubber Washers for Industrial Machinery and Equipment](https://img.engineeringhardware.com/OEM-Black-Nylon-Insulating-Flat-Plastic-Spacer-Anti-Vibration-Silicone-Rubber-Washers-for-Industrial-Machinery-and-Equipment.webp)](https://engineeringhardware.com/product/oem-black-nylon-insulating-flat-plastic-spacer-anti-vibration-silicone-rubber/)

Wedge-Lock & Anti-Vibration Washers

### [OEM Black Nylon Insulating Flat Plastic Spacer Anti Vibration Silicone Rubber Washers for Industrial Machinery and Equipment](https://engineeringhardware.com/product/oem-black-nylon-insulating-flat-plastic-spacer-anti-vibration-silicone-rubber/)

Silicone Rubber, EPDM, NBR, FKM, Silicone · Wiper Seal

**US$0.06 – 1.45**MOQ 100 pieces

[View all Wedge-Lock & Anti-Vibration Washers →](https://engineeringhardware.com/fastener-products/washers/wedge-lock-anti-vibration-washers/) [Full product catalog](https://engineeringhardware.com/products/)

## Materials & Grades

Select a material class to see the grades we supply it in. Each designation is listed with its ISO/EN, AISI/SAE, JIS and GB equivalents.

Stainless Steel38 Carbon Steel66 Alloy Steel41 Bearing Steel5 Spring Steel25 Aluminum and Aluminum Alloys21 Brass17 Bronze11 Copper8 Titanium and Titanium Alloys18 Nickel and Nickel Alloys22 Iron-Nickel and High-Temperature Alloys10 Tool Steel and Specialty Hardened Steel9 Structural and Construction Steel9

### Stainless Steel

#### Austenitic Stainless Steel

- A1 AISI 303 · SAE 303 · SUS303 · EN 1.4305 · X8CrNiS18-9
- A2 AISI 304 · SAE 304 · SUS304 · EN 1.4301 · X5CrNi18-10 · 06Cr19Ni10
- 304L AISI 304L · SUS304L · EN 1.4307 · X2CrNi18-9 · 022Cr19Ni10
- 302 AISI 302 · SUS302 · EN 1.4310
- 305 AISI 305 · SUS305 · EN 1.4303
- A4 AISI 316 · SAE 316 · SUS316 · EN 1.4401 · X5CrNiMo17-12-2 · 06Cr17Ni12Mo2
- 316L AISI 316L · SUS316L · EN 1.4404 · X2CrNiMo17-12-2 · 022Cr17Ni12Mo2
- 321 AISI 321 · SUS321 · EN 1.4541 · X6CrNiTi18-10
- 310 / 310S AISI 310 · AISI 310S · SUS310S · EN 1.4845
- 302HQ AISI 302HQ
- A3
- A5
- 347 AISI 347 · SUS347 · EN 1.4550 · X6CrNiNb18-10
- 309 / 309S AISI 309 · AISI 309S · SUS309S

#### Martensitic Stainless Steel

- AISI 410 SUS410 · EN 1.4006 · X12Cr13 · 12Cr13
- AISI 420 SUS420J1 · SUS420J2 · EN 1.4021 · EN 1.4028 · 20Cr13 · 30Cr13
- AISI 431 SUS431 · EN 1.4057 · X17CrNi16-2
- C1
- C3
- C4
- AISI 440A
- AISI 440B
- AISI 440C SUS440C · EN 1.4125

#### Ferritic Stainless Steel

- AISI 430 SUS430 · EN 1.4016 · X6Cr17 · 10Cr17
- F1
- AISI 434
- AISI 444

#### Precipitation-Hardening Stainless Steel

- 17-4 PH AISI 630 · UNS S17400 · SUS630 · EN 1.4542 · X5CrNiCuNb16-4
- 15-5 PH UNS S15500
- 17-7 PH UNS S17700

#### Duplex and Super Duplex Stainless Steel

- Duplex 2205 UNS S31803 · UNS S32205 · EN 1.4462
- Super Duplex 2507 UNS S32750 · EN 1.4410
- D2
- D4
- D6
- D8
- Lean Duplex 2101 UNS S32101
- Super Duplex S32760 UNS S32760 · EN 1.4501

### Carbon Steel

#### Low-Carbon Steel

- SAE 1006
- SAE 1008
- SAE 1010
- SAE 1018
- SAE 1020
- Q195
- Q235
- SAE 1012
- SAE 1015
- Q215
- ML08
- ML08Al
- ML10
- ML15
- ML20
- SWRCH6A
- SWRCH8A
- SWRCH10A
- SWRCH12A
- SWRCH15A
- SWRCH18A

#### Medium-Carbon Steel

- SAE 1035
- SAE 1045
- S45C
- C45
- SAE 1030
- SAE 1040
- SAE 1050
- 30
- 35
- 40
- 45
- 50
- S35C
- S40C
- S50C
- C35
- C40

#### High-Carbon Steel

- SAE 1060
- SAE 1070
- 65Mn
- SAE 1065
- SAE 1075
- SAE 1080
- SAE 1085
- SAE 1090
- SAE 1095
- 60
- 65
- 70
- 75
- 80
- 85

#### Cold-Heading Steel

- SWRCH22A
- 10B21
- SWRCH22K
- SWRCH25K
- SWRCH30K
- SWRCH35K
- SWRCH40K
- ML20Mn
- ML25
- ML30
- ML35
- ML40
- 15B25

### Alloy Steel

#### Chromium Steel

- 40Cr
- 45Cr
- AISI 5140
- SAE 5140
- AISI 5120
- SAE 5120
- SCr420
- SCr440

#### Chromium-Molybdenum Steel

- 35CrMo
- 42CrMo
- AISI 4140
- SCM435
- SCM440
- 42CrMo4
- 30CrMo
- AISI 4130
- SAE 4130
- SAE 4140
- AISI 4142
- AISI 4145
- SCM415
- SCM420
- SCM445
- EN 1.7220
- EN 1.7225
- 25CrMo4
- 34CrMo4

#### Nickel-Chromium-Molybdenum Steel

- AISI 4340
- SAE 4340
- 40CrNiMo
- SNCM439
- EN 1.6511
- 36CrNiMo4

#### Boron Alloy Steel

- 10B22
- 10B21
- 15B21
- 15B25
- 20MnTiB
- 20Mn2B
- 35VB
- 40MnB

### Bearing Steel

#### Bearing Steel

- GCr15
- AISI 52100 SAE 52100 · UNS G52986
- SUJ2
- 100Cr6 EN 1.3505
- GCr15SiMn

### Spring Steel

#### Carbon Spring Steel

- SAE 1065
- SAE 1070
- SAE 1075
- SAE 1080
- SAE 1095
- 65
- 70
- 75
- 80
- 65Mn

#### Silicon-Manganese Spring Steel

- 60Si2Mn
- 60Si2MnA
- SUP6
- SUP7

#### Chromium-Vanadium Spring Steel

- 50CrVA
- SAE 6150
- AISI 6150
- SUP10

#### Stainless Spring Steel

- AISI 301
- SUS301
- EN 1.4310
- AISI 302
- AISI 304
- AISI 316
- 17-7 PH

### Aluminum and Aluminum Alloys

#### Commercially Pure Aluminum

- 1050
- 1060
- 1070
- 1100

#### 2xxx Series Aluminum

- 2024
- 2011
- 2014
- 2017

#### 5xxx Series Aluminum

- 5052
- 5083
- 5754

#### 6xxx Series Aluminum

- 6061
- 6061-T6
- 6063
- 6082
- 6082-T6

#### 7xxx Series Aluminum

- 7075
- 7075-T6
- 7005
- 7050
- 7075-T73

### Brass

#### Free-Cutting Brass

- C36000
- H62
- HPb59-1
- C3601
- C3602
- C3604
- CuZn36Pb3
- CuZn39Pb3
- EN CW614N
- EN CW617N
- H65

#### Lead-Free Brass

- C69300
- C27450
- CW510L
- CW511L

#### Naval Brass

- C46400
- CuZn39Sn1

### Bronze

#### Silicon Bronze

- C65500
- C65100
- C65600

#### Phosphor Bronze

- C51000
- C52100
- CuSn6
- CuSn8

#### Aluminum Bronze

- C95400
- C95500
- C63000
- CuAl10Ni5Fe4

### Copper

#### Copper

- C11000
- T2
- C10100
- C10200
- C12200
- T1
- TU1
- TU2

### Titanium and Titanium Alloys

#### Commercially Pure Titanium

- Grade 2
- Grade 1
- Grade 3
- Grade 4
- TA1
- TA2
- TA3

#### Alpha-Beta Titanium Alloys

- Grade 5
- Ti-6Al-4V
- TC4
- UNS R56400

#### Low-Interstitial Grade

- Grade 23
- Ti-6Al-4V ELI
- UNS R56407

#### Other Titanium Fastener Alloys

- Ti-6Al-6V-2Sn
- Ti-6Al-2Sn-4Zr-2Mo
- Beta-C titanium
- Ti-10V-2Fe-3Al

### Nickel and Nickel Alloys

#### Commercially Pure Nickel

- Nickel 200
- UNS N02200
- Nickel 201
- UNS N02201

#### Inconel Alloys

- Inconel 625 UNS N06625
- Inconel 718 UNS N07718
- Inconel 600 UNS N06600
- Inconel 601 UNS N06601
- Inconel 686 UNS N06686
- Inconel X-750 UNS N07750

#### Monel Alloys

- Monel 400 UNS N04400
- Monel K-500 UNS N05500

#### Hastelloy Alloys

- Hastelloy C-276 UNS N10276
- Hastelloy C-22 UNS N06022
- Hastelloy B-2 UNS N10665
- Hastelloy B-3 UNS N10675
- Hastelloy X UNS N06002

#### Other Nickel Alloys

- Alloy 20 UNS N08020
- Alloy 625
- Alloy 718
- Alloy 825 UNS N08825
- Alloy 925 UNS N09925

### Iron-Nickel and High-Temperature Alloys

#### A286

- A-286
- UNS S66286
- EN 1.4980

#### Invar

- Invar 36
- Alloy 36
- UNS K93600
- FeNi36

#### Alloy 42

- Alloy 42
- UNS K94100
- FeNi42

### Tool Steel and Specialty Hardened Steel

#### Tool Steel and Specialty Hardened Steel

- AISI D2
- AISI H13
- SKD11
- Cr12MoV
- AISI O1
- AISI A2
- AISI S7
- SKD61
- 9CrSi

### Structural and Construction Steel

#### Structural and Construction Steel

- ASTM A36
- Q235B
- Q355B
- S355JR
- Q235C
- Q355C
- S235JR
- S275JR
- S355J2

## Applications & Industries

The sectors that buy Wedge-Lock Washer Pairs, and the duty each one buys them for. Stocked from M6 to M20 (nominal bolt size).

### Industries that specify Wedge-Lock Washer Pairs

- **Safety-critical joints:** Connections that cannot be re-torqued in service.
- **Mobile & off-highway:** Joints under continuous dynamic load.
- **Vibrating machinery:** Compressors, screens, crushers and rail equipment.
- **Machine building & OEM:** Setting bearing area on soft alloy, plastic and oversized holes.
- **Timber & construction:** Large-diameter washers that stop pull-through in softer material.
- **Rotating & vibrating plant:** Spring, tooth and wedge types that maintain or lock bolt tension.

### Typical applications

- always fitted as a pair with the cam faces together
- locking by cam geometry rather than by friction
- protecting a painted or plated surface under a turned nut
- maintaining bolt tension in a joint that settles
- spreading clamp load over a soft or oversized bearing face

### Service conditions to specify against

- **Marine and coastal:** Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- **Vibration:** Specified where cyclic load would loosen a plain nut or screw — rotating plant, rail, mobile equipment and anything that is not re-torqued in service.
- **Hardness matters:** Under a high-strength bolt a soft washer embeds into the joint and preload is lost — specify a hardened washer for structural bolting.

### Where to use something else

- A single washer from a pair is just a serrated washer and does none of the locking.

[Full application guide: where Wedge-Lock Washer Pairs are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/wedge-lock-washer-pairs/)

## Technical Drawing

Dimensioned line drawing of M6 Wedge-Lock Washer Pairs to Trade series (cam wedge-lock pair). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Inner diameter d1 (mm):** 6.4
- **Outer diameter d2 (mm):** 10.8
- **Thickness of pair t (mm):** 2.5
- **Cam angle:** approx. 12°
- **Fits property class up to:** 12.9
- **Material:** Hardened steel, Delta Protekt
- **Re-use:** Yes, teeth permitting

## Dimensions & Specifications (Trade series (cam wedge-lock pair))

Every row below is a starting point for the customizer above — pick any size and the drawing will redraw to that row.

| For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness of pair t (mm) | Cam angle | Fits property class up to | Material | Re-use |
| --- | --- | --- | --- | --- | --- | --- | --- |
| [M6](https://engineeringhardware.com/guide/size/m6-wedge-lock-washer-pairs/) | 6.4 | 10.8 | 2.5 | approx. 12° | 12.9 | Hardened steel, Delta Protekt | Yes, teeth permitting |
| [M8](https://engineeringhardware.com/guide/size/m8-wedge-lock-washer-pairs/) | 8.7 | 13.5 | 3.4 | approx. 12° | 12.9 | Hardened steel, Delta Protekt | Yes, teeth permitting |
| [M10](https://engineeringhardware.com/guide/size/m10-wedge-lock-washer-pairs/) | 10.7 | 16.6 | 3.4 | approx. 12° | 12.9 | Hardened steel, Delta Protekt | Yes, teeth permitting |
| [M12](https://engineeringhardware.com/guide/size/m12-wedge-lock-washer-pairs/) | 13.0 | 19.5 | 4.0 | approx. 12° | 12.9 | Hardened steel, Delta Protekt | Yes, teeth permitting |
| [M16](https://engineeringhardware.com/guide/size/m16-wedge-lock-washer-pairs/) | 17.0 | 25.4 | 4.6 | approx. 12° | 12.9 | Hardened steel, Delta Protekt | Yes, teeth permitting |
| [M20](https://engineeringhardware.com/guide/size/m20-wedge-lock-washer-pairs/) | 21.4 | 30.7 | 5.2 | approx. 12° | 12.9 | Hardened steel, Delta Protekt | Yes, teeth permitting |

Manufactured to Trade series (cam wedge-lock pair), Wedge-Lock Washer Pairs are washers supplied by Engineering Hardware. The dimensional data, materials and selection notes are summarized here.

## What Are Wedge-Lock Washer Pairs?

Wedge-Lock Washer Pairs are washers defined by Trade series (cam wedge-lock pair). They are selected by nominal bolt size and the dimensional characteristics shown below, and are available in a range of materials and finishes to suit the application and environment.

## Materials & Finishes

Common materials include carbon steel (typically zinc plated or hot-dip galvanized), hardened or case-hardened steel where wear matters, and stainless steel A2 (304) or A4 (316) for corrosion resistance. Specify the material, hardness where relevant, and the surface finish appropriate to your application and environment.

## Specification Guides

Each size, material and standard of Wedge-Lock Washer Pairs has its own reference page with the figures for that one configuration.

## Goes With

Hardware commonly specified alongside Wedge-Lock Washer Pairs.

## Pricing

Wedge-Lock Washer Pairs are supplied to order. Pricing starts from approximately US$0.28 per piece for standard sizes in carbon steel; final pricing depends on size, material, finish and order quantity (MOQ applies). Submit your exact configuration with the quote form above.

Custom manufacturing · Made to drawing

## Need a wedge-lock washer pairs outside the standard range?

Bore, outside diameter, thickness, temper and finish are the variables here — there is no thread to specify, so the fit and the bearing area are what the drawing has to pin down. Made by stamping or punching.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

[Custom washer manufacturing](https://engineeringhardware.com/custom/washers/)[Send a drawing](https://engineeringhardware.com/custom/washers/#rfq)

Inside the plant

## Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift.
2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g.
3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1.
4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227.

## Frequently Asked Questions

### What standard are Wedge-Lock Washer Pairs manufactured to?

Wedge-Lock Washer Pairs are manufactured to Trade series (cam wedge-lock pair). The dimensional values on this page follow that standard.

### Which sizes of Wedge-Lock Washer Pairs does Engineering Hardware supply?

The table on this page lists 6 sizes for Wedge-Lock Washer Pairs, ranging from M6 to M20. Sizes outside the table can be quoted on request.

### In which materials are Wedge-Lock Washer Pairs supplied?

Wedge-Lock Washer Pairs are supplied in carbon steel (zinc plated / HDG) and stainless A2 / A4, with finishes including zinc plating, hot-dip galvanizing and black oxide. Choose material and finish to suit the load and the service environment for Wedge-Lock Washer Pairs.

### How do I request a quotation?

Use the parametric drawing on this page to set the exact configuration (size, material, finish) and click "Request this configuration" — a specialist from Engineering Hardware will respond within one business day.