Our fuel filters are designed to be used in conjunction with each other. The primary filter should be placed between the tank and the pump and will collect all of the major debris before it has a chance to damage the pump. This filter is a 100 micron stainless steel cartridge type filter which can be easily cleaned and reused. The compact in line filter should be placed between the fuel pump and the carburetor or injector nozzles. This is a 40 micron stainless mesh screen type filter which should be cleaned on a regular basis.