Twin Air 158186c Power Flow Air Filter Kit Fits: Husaberg 390 FE 2012, 450/570 FE 09-12 The best filter in the world can't do its job if there are leaks in the seal of the air box Twin Air power flow kit for 4-Stroke models increases air flow while maintaining safety Replaces your air-restricting stock backfire screen with the power flow kit The kit includes a rigid, lightweight, billet aluminum cage with a special backfire-resistant layer of foam laminated to the inside of the filter