Pololu Wheel 60×8mm Pair for FEETECH FS90R/FT90R Micro Servo - Black
These black plastic wheels are designed specifically for use with FT90R digital micro continuous rotation servos. The wheels have silicone tires and measure 60 mm (2.36″) in diameter. Two additional mounting holes for 4-40 screws make it possible to use the wheel with several of our universal mounting hubs. The wheels are sold in pairs.
more info at the Pololu Website