Parker A-Lok 4BC4-B Brass Compression Tube Fitting, Bulkhead Union, 1/4" Tube OD Bulkhead union mounts on a wall or bulkhead to allow connections on either side of barrier Fitting connects to tubing on either side of a bulkhead Brass for corrosion resistance, ductility at high temperatures, and low magnetic permeability Hex nut construction for tighter, leak-free connections Compatible with stainless steel, copper, rigid and semi-rigid plastic tubing