Brass o/a; valve has poppet type check; valve closes if system pressure is dumped into the gage preventing gage from being damaged, valve is also equipped w/safety relief valve set at 15 psi; 2 int thd pipe connections, 0.250-18 npt-rh thd size; 2.115 in.O/a lg, 1.740 in. O/a h, 1.150 in. O/a w