Ball check valves are available in brass maximum operating pressure of 2000 PSI. 1/2MNPT or 3/4 FNPT. 1/2 MNPT has seals of Buna/FKM/EPDM, and FKM only for 3/4 valves. Electroless nickel plating is available. Overall cracking pressure is between 1-5 PSI standard. 1/2 Male unit offered in less than 1, or more than 5 PSI. Both units are available without springs.