Filter Bag Housings for the Pentek BP-420-25 Bag Filter: The Pentek BP-420-25 155390-03 bag filter fits in bag filter housing assemblies for 4" W x 18" L bag filters. Use the Pentek PBH-420-1 1" Inlet/Outlet Bag Filter Vessel Water Filter System. Use the Pentek PBH-420-1.5 1.5" Inlet/Outlet Bag Filter Vessel Water Filter System. Pentek BP-420-25 Bag Filters Also Known As: American Plumber BP-420-25 Filter Bags Ametek BP-420-25 Filter Bags Plymouth Products BP-420-25 Filter Bags Pentek 155390, 155390-03 Filter Bags USFilter BP-420-25 Filter Bags . . (Package Of 5)