Contoured Back-Ups are routinely produced in a 90 durometer Nitrile - Buna-N. This provides sufficient elasticity to permit stretching over the major diameter of a piston and then snapping back into the gland groove cut into the piston. 90 durometer has sufficient hardness to resist extrusion of the softer elastomeric O-Ring performing the actual sealing function against the high pressure liquid or gas.

- 000 Series O-rings 0.070" ±0.003" - .045" Thick
- 100 Series O-rings 0.103" ±0.003" - .045" Thick
- 200 Series O-rings 0.139" ±0.004" - .040" Thick
- 300 Series O-rings 0.210" ±0.005" - .060" Thick
- 400 Series O-rings 0.275" ±0.006" - .096" Thick
NOTE: Sizes (Dash No.) corresponds to standard O-ring numbers.