S&S Cycle Black Oil Filter 31-4103 Constructed in a sturdy steel canister which houses the finest filtering media and internal components Slightly smaller in diameter than stock to allow for easier removal and installation Includes bypass valve to keep oil flowing even when it can't go through he media quick enough Direct bypass minimizes the amount of contaminants carried to the engine in the unfiltered bypass oil since the oil is not allowed to pick up contaminants by flowing over the dirty side of the filter media Media designed to trap the smallest possible particles while maintaining the lowest restriction to oil flow