Features:* The function of the piston ring is to maintain the tightness between the piston and the cylinder wall.* With the standard size of inner and outer diameter, it is convenient to install and disassemble.* The surface has no casting defects such as cracks, pores, clearance, etc., ensuring a tight connection.* The kit includes 3 spare piston rings (including 2 pcs. Balance ring + 1 pc. O-ring), which can replace the old or damaged ones on the air pump at any time.* Suitable for air compressor and air pump with cylinder diameter 42mm/47mm/48mm/51mm/52mm/65mm, and should be replaced when the axial clearance is greater than 0.13mm. Specifications:* Item Type: Air Compressor Piston Ring * Compatible for: Air Compressor * Size: As the picture shown * Suitable Cylinder Diameter: 42mm 47mm 48mm 51mm 52mm 65mm, please choose the right size.* Quantity: 3pcsPackage Contents:3 x Air Compressor Piston RingNote:1. The actual colors of the item may be slightly different from the pictures shown on website caused by many factors such as brightness of your monitor and light brightness.2. Please allow slight manual measurement deviation for the data.