Npt national pipe thread seals are the top choice among customers type of seal for pressure calibration frameworks within the u. S. And canada. Npt male adapters have a taper thread that wedges into the female npt adapter. They seal because of the out of roundness principle which means that the male stretches the female fitting until there is so much force that the connection can hold pressure. A leading choice of the challenges with this design is that if you connect stainless steel to stainless steel then over, Tightening or poor lubrication can cause gauling and damage to the threads. Thread sealant is needed to seal but only 2 turns of thread sealant is required. Any more than that and the seal can leak around the thread sealant. Mcneil instruments inc has a broad assortment of male npt adapters, Male quick, Female npt adapters, Female npt disconnect npt, Gauge adapters adapters, Male npt calibrator adapters and female quick, Disconnect npt gauge adapters. Quickly connect a pressure calibrator or other pressure device with female npt connections to ralston hand pumps or nitrogen calibration equipment