EPDM rubber is a terpolymer of ethylene, propylene and diene monomers. O rings manufactured from EPDM exhibit an excellent resistance to weathering and ozone, water and steam. General purpose EPDM O rings are manufactured using a sulphur based curing system, these are suitable for use up to +120°C whereas peroxide cured O rings can be used up to +150°C. EPDM is particularly useful when sealing in brake systems that use fluids having a glycol (Dot 3 and 4) or silicone base (Dot 5). Polymax peroxide cured EPDM O-ring have a series of approvals including ACS, WRAS, KTW, EN 681-1.