Fram, P3401, Primary Spin On, Fuel Filter, Application Specific Media Designed To Meet The Needs Of Each Engine, Primary Filters Are Designed For Balance Between Low Restriction & Required Efficiency, Secondary Filters Are Designed For Maximum Particle Removal To Prevent Wear In Injectors, Pumps & Valves, Designed As A Fuel System Primary & Secondary Working Together For Optimum Fuel System Performance, Filter Bodies & Bottom Plates Are Engineered To Resist Pressure & Vibrations Encountered In Use.