High Pressure Brass Check Valves, all purpose check valve for water applications, will operate in any position; 1/3 PSI standard cracking pressure; 500 PSI maximum operating pressure; 180 degrees Fahrenheit maximum operating temperature; body are brass and the floating disc is made of brass and Nitrile rubber (Buna-N) for a bubble-tight seal. In the reverse flow, the fluid pushes the disc ahead of it until the face of the disc's ring comes in contact with the sealing seat shutting the nflow. As the pressure builds up, the Buna-N ring is compressed for a positive seal