Catalog › O-Rings and Gaskets
O-Ring Sizes, O-Ring Cord and Gaskets
O-rings in NBR and FKM (Viton) in metric and inch sizes. Cylinder seals, rod seals and wipers are a separate group.
The O-ring is the most common type of seal, sealing by being compressed between two mating surfaces. Two values determine the correct selection: size (inner diameter × cross-section diameter) and material.
Material selection depends on the fluid and the operating temperature. NBR is the standard choice for general hydraulic oils and operates roughly between -30 °C and +100 °C. FKM (Viton) is used for high temperatures and aggressive fluids. EPDM is suitable for water and brake fluid but must never be used with mineral oil — this is the most common material mistake made in the field.
The O-ring is only one part of a complete sealing set. The nutrings, piston seals, wipers, and wear rings that do the main work in hydraulic cylinders form a separate category and make up a much larger share of our stock (5,297 items); see the «Hydraulic Seals, Nutrings and Wipers» page for those.
Brands and standards in stock
Don't see the brand you're after? Ask anyway — o-rings and gaskets products are made to standard, so different brands carrying the same standard are equivalents.
O-Rings and Gaskets in stock — examples
| Product | Brand | Model / size | Manufacturer code |
|---|---|---|---|
| O-RİNG 20,35 x 1,78 | Kastaş | 20,35 x 1,78 | KO-0203517 |
| O-RİNG 69,52 x 2,62 | Kastaş | 69,52 x 2,62 | KO-0695226 |
| O-RİNG 75,00 x 3,00 | Kastaş | 75,00 x 3,00 | KO-0750030 |
| O-RİNG 17,13 x 2,62 | Kastaş | 17,13 x 2,62 | KO-0171326 |
| O-RİNG 34,52 x 3,53 | Kastaş | 34,52 x 3,53 | KO-0345235 |
| O-RİNG 31,47 x 1,78 | Kastaş | 31,47 x 1,78 | KO-0314717 |
| O-RİNG 7,66 x 1,78 | Kastaş | 7,66 x 1,78 | KO-0076617 |
| O-RİNG 6,00 x 2,00 | Kastaş | 6,00 x 2,00 | KO-0060020 |
| O-RİNG 4,48 x 1,78 | Kastaş | 4,48 x 1,78 | KO-0044817 |
| O-RİNG 17,86 x 2,62 | Kastaş | 17,86 x 2,62 | KO-0178626 |
| O-RİNG 5,23 x 2,62 | Kastaş | 5,23 x 2,62 | KO-0052326 |
| O-RİNG 24,99 x 3,53 | Kastaş | 24,99 x 3,53 | KO-0249935 |
| O-RİNG 5,28 x 1,78 | Kastaş | 5,28 x 1,78 | KO-0052817 |
| O-RİNG 15,00 x 3,00 | Kastaş | 15,00 x 3,00 | KO-0150030 |
| O-RİNG 6,02 x 2,62 | Kastaş | 6,02 x 2,62 | KO-0060226 |
| O-RİNG 15,08 x 2,62 | Kastaş | 15,08 x 2,62 | KO-0150826 |
| O-RİNG 57,15 x 3,53 | Kastaş | 57,15 x 3,53 | KO-0571535 |
| O-RİNG 29,75 x 3,53 | Kastaş | 29,75 x 3,53 | KO-0297535 |
| O-RİNG 43,00 x 2,00 | Kastaş | 43,00 x 2,00 | KO-0430020 |
| O-RİNG 20,22 x 3,53 | Kastaş | 20,22 x 3,53 | KO-0202235 |
| O-RİNG 42,52 x 2,62 | Kastaş | 42,52 x 2,62 | KO-0425226 |
| O-RİNG 44,04 x 3,53 | Kastaş | 44,04 x 3,53 | KO-0440435 |
This list is sorted by our highest-moving items and isn't the whole of our 952-item o-rings and gaskets stock. If the size you need isn't listed, we very likely have it — just ask.
Frequently asked questions
How do I read an O-ring size?
O-ring size is given as inner diameter × cross-section (cord) diameter. For example, 20×2.5 means a 20 mm inner diameter and a 2.5 mm cross-section. Measurement should be taken unstretched, preferably with calipers; a used O-ring may be permanently deformed, which makes its measured size misleading.
Should I choose NBR or FKM?
For standard mineral-based hydraulic oil at normal operating temperatures, NBR is sufficient and more economical. FKM is preferred in applications where temperature is continuously above 100 °C, or where there is contact with fuel or chemicals.
Why is EPDM not used with hydraulic oil?
EPDM swells on contact with mineral oil and loses its sealing properties. It is the correct choice for water-based fluids and brake fluid; mineral-oil systems should use NBR or FKM instead.
Get a quote for O-Rings and Gaskets
Send us the size and quantity you need and our sales team will get back to you the same day with pricing and lead time. If you're not sure of the size, a photo of the part you have is enough.