They are used in all those situations where the full flow in one way and the stop on the opposite way are needed. The sizes are from 1/4 BSPP (1/4 G) to 1 BSPP (1 G). This check valve with tapered poppet or ball is useful in small places or to compact the hydraulic installations. The coupling is made by high resistance steel and externally protected from oxidations by zinc treatment. Different opening than the standard one (1 bar) are possible: 3-4.5-6 bar.