This 12-bolt Fill Valve with Check Valve Flapper can be retrofitted to bolt onto any of our standard 12-hole pattern cap assemblies. It has a 2-1/4" O.D. fill tube and twist-lock cap. It features a bolted-in plastic flapper for rollover protection and comes standard with an AN-10 Tip Over Valve Vent fitting. Designed to be used on fuel cells with or without safety foam installed. This is IMCA approved, made to reduce the cost for customers who require rollover protection, but do not want the extra cost of a spring-loaded flapper. Fuel cells built with this new filler installed will also come with a bat wing attached to the pick-up hose to prevent the hose from curling or moving.