Front and Back Disk Brake Kit - 160mm For 80cc Gas Motorized Bicycle Complete 26" Mechanical Disk Brake Kit, Front and Back - 160mm rotor diameter. Center 6 bolt pattern diameter on rotor is 1.75 Inches. This kit comes with 2 mounting adapter, your hub need to either have the same 6 bolt pattern to mount the rotor directly or you can use the mounting adapter on your threaded hub (1.37 x 24 tpi). This kit works best with our motorized bicycle frames and KMB frames. Caliper Holders are NOT included but are required.