2 Pcs Piston Ring Oil-Less AB-9040019 For Husky Bostitch Air Compressor CAP2000P CAP2040P CAP1512 CAP60PB CAP60P Fits Models: H27508UWK / A600006. Does NOT fit the "WL" or other series units. Part Numbers: AB-9040019, AB9040019 40mm ID. This is for the 50mm Cylinder Bore. This part is installed on top of the piston/connecting rod.Its purpose is to create a seal in the cylinder so that air can be pump into the compressor tank. If this part wears your compressor will not pump the air properly.This is a wear part and it is advised to keep an extra one on hand. This part is compatible with the following machines: Bostitch CAP2000P-OF Type 0 Air Compressor CAP2040P-OF Air Compressor CAP60P-OF Air Compressor CAP60PB-OF Air Compressor CAP1512-OF (Type 0) Air Compressor