Upgraded torque e-bike brake rotor spacerthese high quality plastic spacers used to space the disc rotor out a little bit more to stop your caliper from rubbing on your hub motor. Mainly used for our 3000w and 5000w kits because the motor is a bit wider. Usually our 5mm spacer works the best as the kits come stock with a 3mm spacer. You need to use longer screws to hold the disc in when using a spacer to not wreck the threads of the disc rotor holes.