Syndyt Expert BMX Bike Chain Tensioner Kit Stainless Steel M6 Tensioner Screws, Aluminum Anodized Adjuster Knob, Compatible with 10mm 15mm 20mm Axle Adaptors String Trimmer Blower combo making it the perfect fit security making it the perfect fit for riders who demand extraordinary from their tires Impact resistant outer case and shock absorbing inner liner are engineered to protect the battery M6 threaded tensioner screws with a cradle to match directly with a 20mm axle or one of the (included with the frame) 10mm or 15mm axle adaptor kits The black anodized adjuster knob is made from aluminum and threads over the tensioner screw