Pololu Wheel for Standard Servo Splines (25T, 5.8mm) - 70×8mm, Black, 2-Pack
These black plastic wheels have silicone tires and measure 70 mm (2.75″) in diameter. They mount onto standard servo splines with 25 teeth and a 5.8 mm diameter, such as the splines on FEETECH’s FS5106R and SpringRC’s SM-S4303R continuous rotation servos. This product is a pair of wheels.
These wheels are great for robotics, custom RC vehicles, or any other project you need to get rolling. The combination can serve as a small, inexpensive, and easy-to-control drive system for a miniature robot. The wheel presses onto the servo spline just like a typical servo horn, and the small screw included with the servo accessory pack for mounting servo horns should be used to hold the wheel in place.