AB-9040019 Husky Air Compressor Piston Ring Oil-Less Oil-less Compressor Piston Ring AB-9040019 Fits Models: H27508UWK / A600006. Does NOT fit the "WL" or other series units. Fits 50mm Cylinder Bore. 40mm ID. This is for the 50mm Cylinder Bore. If you are unsure if this is the correct piston ring, please send us your model type / serial number and we will be happy to help.