.125 PSI springs are not recommended for installations with flow vertical down.
Seat materials other than “metal-to-metal” have a maximum pressure rating of 1500 PSI. “Metal-to-Metal” and PTFE seats are not resilient. See allowable leakage (New window will open).
The bushing thread sizes are designated by two sets of numbers; the first being the male thread, the second the female thread. NPT threads are per ASME B1.20.1.