These check valves are made for use on 1 1/2" or larger scale locomotives. Available in 2 sizes: 1 11/16" tall (1/4" tubing and threaded 1/8 NPT) and about 2" tall (5/16" tubing and threaded 1/4 NPT). Both valves use Buna-N seats with a piloted check valve which gives very positive sealing. The valve is easily serviced and does not require the attention to seat integrity that a ball check requires. You will find these valves to be up to any duty you may required of them.