The surplus units were widely used in fuel systems for decades. However, the surplus synthetic rubber seals are not always compatible with current hydrocarbon fuels and/or additives. Earl’s has redesigned the original surplus valves with modern elastomers which are not affected by most fuels and lubricants. Unaffected By Most Fuels. Unaffected By Most Lubes. Earls 251006ERL Check Valve Flapper Style, Reinforced Viton -6 AN. Aluminum Support on Seal. Related Items / Suggested Parts. Earls 251010ERL Check Valve Flapper Style, Reinforced Viton -10 AN. Speedway Motors is America’s Oldest Speed Shop® and has been a trusted source for specialty rodding and racing products and friendly expert advice for more than 72 years.