EK PBR Chain kit 520 SRX2 13 49 116 Alu Standard Rear Sprocket Hoodies sweatshirts and sweat jackets billet aluminum cage with a billet aluminum cage with a special backfire resistant layer of foam laminated to the inside of the filter The TWINAIR Power Flow kit has an aluminum cage that strengthens the filter and provides maximum seal earning it widespread popularity among diverse riders it continuously evolves with regular enhancements incorporating cutting edge technology