WIX Filters - 33804 Heavy Duty Spin On Fuel Water Separator, Pack of 1 WIX 33804 WIX Spin-On Fuel/Water Separator Filter Principle Application: Caterpillar, Equipment w/ Perkins 4.4L engines - Cat OE (1R1804) is a threaded cartridge - 33804 is a spin-on that includes the outer shell - the OE outer shell is no longer required with our filter -for shorter version, use WF10105 Packaged Individually