Feature:1. The function of the piston ring is to maintain the air tightness between the piston and the cylinder wall.2. With standard inner and outer diameter size, it is convenient to install and disassemble.3. The surface has no casting defects such as cracks, pores, looseness, etc., ensuring tight connection.4. The kit contains 3 replacement piston rings, which can replace the old or damaged ones on the air pump at any time.5. Suitable for air compressors and air pumps with a cylinder diameter of 55mm, and need to be replaced when the axial clearance is greater than 0.13mm.Specification:Item Type: Air Compressor Piston RingModel: 55 Piston RingDrive Mode: PneumaticPiston Ring Outer Diameter: 58mm / 2.3inPiston Ring Inner Diameter: 52mm / 2inApplicable Models: Approx. 55mm / 2.2in cylinder diameter 1P/2.5P/3P/4P/5P for Outstanding/Jaguar air compressor air pump accessories.Package List:3 x Air Compressor Piston RingNote:The number 55 means that the cylinder diameter is 55mm.