MIL-PRF-25675C, PERFORMANCE SPECIFICATION: VALVES, CHECK, MINIATURE, HYDRAULIC, AIRCRAFT AND MISSILE (26 NOV 1997) [SUPERSEDES MIL-V-25675B, MS24423C AND MS24593D]., This specification covers hydraulic, spring-loaded, normally closed aircraft and missile hydraulic system check valves with operating pressures up to 3,000 pounds per square inch (psi) and operating temperatures from -65 deg to 450 deg F.