--- title: "Silicone (VMQ) Metric O-Rings (ISO 3601)" description: "Silicone (VMQ) Metric O-Rings (ISO 3601) (vinyl-methyl silicone, typically 70 Shore A): inert and physiologically neutral; low tear and abrasion strength." url: https://engineeringhardware.com/guide/material/silicone-metric-o-rings/ source: Engineering Hardware & Fasteners --- # Silicone (VMQ) Metric O-Rings (ISO 3601) Seals · ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections) Temperature range, chemical and fluid compatibility, hardness and the full dimensional range for this compound. Silicone (VMQ) Metric O-Rings (ISO 3601) are supplied to vinyl-methyl silicone, typically 70 Shore A. Corrosion behaviour is inert and physiologically neutral; low tear and abrasion strength, the material is non-magnetic, and the usable service range is approx. -60 °C to +200 °C. In practice this grade is used for wide temperature range and food/medical contact, in static seals only. - **Grade:** vinyl-methyl silicone, typically 70 Shore A - **Corrosion resistance:** Inert and physiologically neutral; low tear and abrasion strength - **Magnetic response:** Non-magnetic - **Service temperature:** approx. -60 °C to +200 °C Property values are typical for the grade. Certified mechanical test data is available on request for production orders. ![Silicone (VMQ) Metric O-Rings (ISO 3601) reference image](https://engineeringhardware.com/wp-content/uploads/2026/09/Metric-O-Rings.webp) Material specification page for metric o-rings (iso 3601) in Silicone (VMQ). Covers the grade designation (vinyl-methyl silicone, typically 70 Shore A), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections). ## Why Choose Silicone (VMQ) for Metric O-Rings (ISO 3601) Used for wide temperature range and food/medical contact, in static seals only. For metric o-rings (iso 3601), this matters when inert and physiologically neutral; low tear and abrasion strength is the primary requirement. ## Mechanical & Physical Properties | Grade designation | vinyl-methyl silicone, typically 70 Shore A | | --- | --- | | Magnetic response | Non-magnetic | | Service temperature | approx. -60 °C to +200 °C | | Corrosion characteristic | Inert and physiologically neutral; low tear and abrasion strength | ## Corrosion Behavior in Service Carbon and alloy steel metric o-rings (iso 3601) require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use. ## Comparable Grades For metric o-rings (iso 3601), consider NBR or FKM wherever the seal is dynamic — silicone has low tear and abrasion strength and is a static-seal material. Elastomer selection is decided by the medium, the temperature range and whether the seal is static or dynamic — not by strength. ## Sizes of Metric O-Rings (ISO 3601) Available in Silicone (VMQ) | Cross-section (mm) | Typical inside-diameter range (mm) | Common compounds | Notes | | --- | --- | --- | --- | | 1.0 | 1.0 – 20 | NBR, FKM, EPDM, silicone | miniature and pneumatic | | 1.5 | 2.0 – 40 | NBR, FKM, EPDM, silicone | small pneumatic and instrument | | 1.78 | 1.78 – 50 | NBR, FKM, EPDM | nearest metric equivalent to the 1/16 in section | | 2.0 | 3.0 – 100 | NBR, FKM, EPDM, silicone | general hydraulic and pneumatic | | 2.5 | 5.0 – 150 | NBR, FKM, EPDM | general hydraulic | | 3.0 | 6.0 – 200 | NBR, FKM, EPDM | general hydraulic | | 3.5 | 10 – 250 | NBR, FKM | hydraulic | | 4.0 | 12 – 300 | NBR, FKM | hydraulic and larger flanges | | 5.0 | 20 – 400 | NBR, FKM | large flanges and covers | | 5.33 | 20 – 400 | NBR, FKM | nearest metric equivalent to the 3/16 in section | | 6.0 | 25 – 500 | NBR, FKM | large covers and housings | Dimensions are independent of the material: every size above is available in Silicone (VMQ). Custom manufacturing · Made to drawing ## Need this seal in a grade that is not listed? Silicone is one of the grades the catalog describes. Inside diameter, cross-section and compound are the three that matter, and the compound is chosen against the fluid and the temperature rather than the dimensions. Minimum order from 2,000 pieces; samples within 7 days of drawing approval. [Custom seal manufacturing](https://engineeringhardware.com/custom/seals/)[Send a drawing](https://engineeringhardware.com/custom/seals/#rfq) ## Technical Drawing Dimensioned line drawing of 1.0 Metric O-Rings (ISO 3601) to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Typical inside-diameter range (mm):** 1.0 – 20 - **Common compounds:** NBR, FKM, EPDM, silicone - **Notes:** miniature and pneumatic ## Dimensions & Specifications (ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections)) | Cross-section (mm) | Typical inside-diameter range (mm) | Common compounds | Notes | | --- | --- | --- | --- | | 1.0 | 1.0 – 20 | NBR, FKM, EPDM, silicone | miniature and pneumatic | | 1.5 | 2.0 – 40 | NBR, FKM, EPDM, silicone | small pneumatic and instrument | | 1.78 | 1.78 – 50 | NBR, FKM, EPDM | nearest metric equivalent to the 1/16 in section | | 2.0 | 3.0 – 100 | NBR, FKM, EPDM, silicone | general hydraulic and pneumatic | | 2.5 | 5.0 – 150 | NBR, FKM, EPDM | general hydraulic | | 3.0 | 6.0 – 200 | NBR, FKM, EPDM | general hydraulic | | 3.5 | 10 – 250 | NBR, FKM | hydraulic | | 4.0 | 12 – 300 | NBR, FKM | hydraulic and larger flanges | | 5.0 | 20 – 400 | NBR, FKM | large flanges and covers | | 5.33 | 20 – 400 | NBR, FKM | nearest metric equivalent to the 3/16 in section | | 6.0 | 25 – 500 | NBR, FKM | large covers and housings | Product catalog ## 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Applications & Industries Where Metric O-Rings are used, and what decides the specification in each case. Stocked from 1.0 to 6.0 (inside diameter). ### Industries that specify Metric O-Rings - **Hydraulics:** Port, cover and piston seals. - **Pneumatics:** Cylinder and valve seals. - **Food and beverage:** EPDM and silicone compounds. - **Chemical plant:** FKM for aggressive media. - **Hydraulics & pneumatics:** Static and dynamic sealing in cylinders and valve bodies. - **Process & food equipment:** Sealing at joints that are cleaned and inspected. ### Typical applications - specifying inside diameter, cross-section and compound together - matching the compound to the fluid and the temperature - checking the groove dimensions give the right squeeze - using a back-up ring at high pressure - sealing a joint against fluid or air pressure - excluding dust and moisture from a housing ### Service conditions to specify against - **Sealed joints:** Used where the fixing has to keep water or air out as well as hold — the elastomer, not the fastener, decides service life. ### Where to use something else - Do not substitute an NBR ring for an FKM one because the dimensions match; the size fits and the compound fails, which looks like a leak with no cause. [Full application guide: where Metric O-Rings are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/metric-o-rings/) 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 ### Are Silicone (VMQ) Metric O-Rings (ISO 3601) magnetic? Silicone (VMQ) Metric O-Rings (ISO 3601) are non-magnetic. ### What corrosion resistance do Silicone (VMQ) Metric O-Rings (ISO 3601) offer? Silicone (VMQ) Metric O-Rings (ISO 3601) provide inert and physiologically neutral; low tear and abrasion strength with a service range of approx. -60 °C to +200 °C. ### Which media is Silicone (VMQ) suitable for? Silicone (VMQ) suits dry heat and cold in static service, and food contact. It is the wrong choice for dynamic duty, fuel and steam — it tears and abrades easily. Elastomer selection is decided by the fluid first, then the temperature, then whether the seal is static or dynamic. ### What hardness are Silicone (VMQ) Metric O-Rings (ISO 3601) supplied in? Shore A 70 is the general-purpose default. A softer compound (around 60) seals better on a rough or slightly out-of-round surface; a harder one (around 80 to 90) resists extrusion at higher pressure or across a wider gap. State the hardness on the order — it is not implied by the material. ### How do I request a quotation? Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day. ## Related Pages [View the full Metric O-Rings (ISO 3601) page](https://engineeringhardware.com/fastener/metric-o-rings/) ### More Metric O-Rings (ISO 3601) Guides