GREAT COMPATIBILITY The AR2546 was used on the Annovi Reverberi RK, RKA, RKV, XRCA, XRV, XRCV, series pressure washer pumps also known as AR pumps. OEM Part #AR2546, Replaces part #2757 KIT CONTAINS 3 PIECE EACH 18mm pistons, backup rings, O ring seals, slingers, washers, and nuts SUPERIOR MATERIAL Made of high-quality ceramic, steel and plastic. Hight precision and Extra-thick ceramic pistons for reater durability. Ceramic Dimensions: 18mm x 40mm, Inside Dimension: 11mm EASY INSTALLATION Remove the old pump piston kit and re-installing the new part back over the rods to maintenance your pressure washer pump. .