[Better Material]Check valves are usually made of PVC,which is suitable for liquid piping systems with and abrasion resistance, good sealing properties. [Compatible with]72351-1/2-Inch to 2-Inch Check Valve For Pools and Spas [Features]Check valves are usually simple in design, compact, take up little space, and the internal passages are usually straight through. [Function]The main function of the check valve is to prevent the medium from flowing backwards, to prevent the pump and drive motor from reversing,and to drain the container medium.