O-Rings are one of the most common seals used in machine design because they are inexpensive and easy to make, reliable, and have simple mounting requirements. They can seal tens of megapascals (thousands of psi) pressure.
O-Rings are manufactured in a vast variety of sizes and compounds.
Imperial sizes AS 568 (Aerospace Standard) have over 360 different sizes in C/S (cross section) and I.D. (inside diameter).
They range from:
| Nominal Cross Section | Actual C/S | Inside Diameter from | Thru Inside Diameter |
| 0 Series 1/16 " C/S |
.070 " C/S | 1/32" | 5 1/4" |
| 1 Series 3/32 " C/S |
.103 " C/S | 1/16" | 9 3/4" |
| 2 Series 1/8 " C/S |
.139 " C/S | 3/16" | 18" |
| 3 Series 3/16 " C/S |
.210 " C/S | 9/16" | 26" |
| 4 Series 1/4 " C/S |
.275 " C/S | 4 1/2" | 26" |
Compounds that are available are extensive. Here are a few base materials.
 Buna'n (Nitrile) |
Butyl |
| Neoprene® |
Hypalon® |
| Fluorocarbon (Viton®) |
Epichlorohydrin |
| EPDM (Ethylene Propylene) |
Teflon |
| Silicone |
Urethane |
| Fluorosilicone |
Aflas |
| Polyacrylate |
Kalrez® |
| Styrene Butadiene (SBR) |
Chemraz |
Metric sizes are available in over 4000 different sizes depending on which country is producing them.
In Germany, Sweden, France, Britain, Italy and Japan, standard dimensions are slightly different from one another.
When there is no standard size to suit your requirements another option is to have your own size and compound made to your own specifications.