SpeedHut F-ADPTR-11 Adapter, 1/4 Inch Npt Male to 7/16 Inch -20 UNF Female

This was a hard adapter to find so good luck finding other suppliers. It took a couple of attempts to get an adapter that worked; the first one I received turned out to be a 1/2-20 UNF and the next one I received was a loose fitting 7/16-20 UNF and began to slip off the threads if I tightened it too much. My gut is that the female part of the threading is lacking in quality control and/or testing to make sure their manufactured products are within tolerance. I simply applied plenty of plumbers tape to help make snug fit. The 1/4 NPT at least was consistently correct.