The Pentek 154171 fits the following housings:
The 154171 1/2" Slim Line 5 Blue Filter Housing Cap is a blue filter housing cap that fits all Pentek Slim Line Sumps housings, including the #5, #10, and #20. This blue filter housing is fitted with a pressure relief valve and is a genuine Pentek part. The bottom cap threads measure 3.86" OD (outer diamater) x 3.153" ID (inner diamater) and do not fit the Pentek 3G Slim Line (SL) filter housings.
154171 1/2" Slim Line 5 Blue Filter Housing Cap specifications: