1、Manufactured by new technology, it can be used for a longer time compared with similar check valve spool. 2、For replace old or damaged check valve core of air compressors, it is an excellent substitute 3、Cylinder heads of oil‑free machines and air compressors can equip with the spring check valve. 4、With high quality material of plastic, it is durable, safe and has a long service life. 5、Check valves are mechanical valves that permit liquids to flow in only one direction, preventing process flow from reversing. 2 x Plastic Plug2 x Spring Item Type: Spring SpoolMaterial: PlasticPlastic Plug Diameter: Approx. 23mm/25mm/27mm/35mm- 0.9in/1in/ 1.1in/ 1.4inPlastic Plug Height: Approx. 12mm/20mm/21mm/30mm- 0.5in/ 0.8in/ 0.83in/ 1.2in