S&S oil filters are constructed in a sturdy steel canister, which houses the finest filtering media and internal components available. The canister is slightly smaller in diameter than stock filters to make them easier to remove and install. S&S filters are designed with a direct bypass valve that routes bypass oil directly to the filter exit. 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, as it is in some competitive filters. The filter media used in S&S oil filters has been selected to trap the smallest possible particles while maintaining the lowest restriction to oil flow. The nominal particle capture size is smaller than that of stock filters while the resistance to oil flow is nearly the same. The most important thing you can do to maximize the life of your engine is to keep your oil clean. Your motor oil picks up friction wear particles and combustion by-products. Regular oil changes are essential to keep contaminants from accumulating, but from one oil change to the next, your oil filter is your first line of defense against these wear causing particles. S&S filters are available in black or chrome finish for use on Evolution style as well as Twin Cam style engines.