Earls stocks "O" ring seals in the traditional Buna N synthetic rubber and in Viton. The Buna compound is compatible with most fuels, hydraulic fluids, and lubricants up to a temperature limit of 275°F. Viton is preferred for synthetic lubricants, oxygen bearing fuels and additives, and non-ether based brake fluids. Viton also has more scuff resistance, a longer service life, and a higher temperature rating of 400°F. (Viton is a registered trademark of DuPont Performance Elastomers).