The 154167 filter housing cap has 1.5 inch NPT inlet and outlet ports. There is a 1-1/4 inch internal port that allows a greater volume of liquid to pass through the cap more rapidly. The 154167 housing top has a red pressure release button that can be used for optional pressure relief or bleed. The 1.5" inlet/outlet filter housing cap is made of high-flow polypropylene. The 154167 water filter housing cap fits #10 Big Blue Polypropylene housings and #20 Big Blue water filter housings.