The custom K&N backing plate included with 2013-2015 Softail air cleaner, number RK-3942, does more than provide a solid mounting surface as it incorporates an integrated crankcase breather system for a trick look that keeps crankcase blow by where it belongs. The entire K&N RK Series Performance air cleaner for 2013-2015 Harley-Davidson Softail models, including the Breakout, Deluxe, Fat Boy, and Heritage remains hidden behind the factory Harley air cleaner cover to ensure only rider and passenger can feel the difference.