This 1/4" - 1/2" check rubber parts replacement kit for series 009 is used for repairing the parts to the relief valve to prevent the reverse flow of polluted water from entering into the potable water supply due to backsiphonage and or backpressure. This kit consists of a disc, cover O-ring and seat O-ring. Made for easy installation and use, it will help ensure the best service life possible.