This 2-5/8" plastic wheel is made specifically for the Solarbotics GM2, GM3, GM8, and GM9 gearbox output shafts, and it also matches the Pololu plastic gearmotors. Each wheel has a silicone tire and 64-stripe encoder pattern molded in.
The GMPW wheel is made to match the Solarbotics GM2, GM3, GM8, and GM9 gearmotors, and it also match the Pololu plastic gearmotors. This plastic wheel is molded from ABS and has a molded-on thermoplastic silicone tire with great traction and wear characteristics. There is a 64-stripe encoder pattern on one side of the wheel compatible with the Wheel Watcher. The plastic wheel measures just under 2-5/8" (69 mm) across by 0.3" (7.62 mm) wide and is available in blue, yellow, red, and black.
(For mini-sumo robots, you can also try using the high-traction sticky tire, which is NOT made to fit this plastic robot wheel, but happens to work pretty well with it.)

Included Parts
One wheel
One screw for mounting to a suitable motor such as those listed under the related products on this page.

Feature Summary
Diameter: just under 2-5/8" (69 mm)
Tire width: 0.3" (7.62 mm)
Tires: molded-on thermoplastic silicone
Encoder stripes: 64-stripe pattern molded in on one side (compatible with the Wheel Watcher)
Color options: blue, yellow, red, and black

Dimensions
Size:  2-5/8" diameter, 0.3" wide 

General specifications
Color:  red