O-Wheels are plastic wheels with a 3/16" thick Buna rubber tire tread. The rubber is rated at 70 Durometer -- hard enough that it doesn't easily deform under the weight of the robot, but pliable enough that it provides grip on most any surface.
O-Wheels are designed to directly attach to any Futaba brand servo, or other make of servo that uses the Futaba spline (Futaba, GWS, Cirrus, Balsa Products, and many others). O-Wheels come in kit form, and are assembled in under five minutes. The plastic materials of the wheels are custom-machined by us.
You have a choice of several different diameters, starting at $4.29 per pair, making these among the least expensive servo-hub wheels available. For most tabletop robots, the 2 1/2" diameter wheels are recommended. This is approximately the same diameter as the plastic wheels used on the Parallax Boe-Bot.