re are four standards of sealing port as follows:Metric thread + O-ring + Retaining O-ring (ISO 9974)Metric thread + O-ring ISO 6149UN/UNF thread + O-ring ISO 11926 SAE J1926 ORBBSPP thread + O-ring + Retaining Ring (ISO 1179)Burst and cyclic endurance(impulse) tests shall be conducted in according with ISO 19879.Dimensions, working pressure, performance, flatness and fit of adjustable studs end washers, O-rings, designations of stud ends, please contact us by email.