Pololu 42x19mm Idler Wheel/Sprocket Pair - Black
The black plastic hubs can be used with the 30T track set as additional idler sprockets, or they can be used with the included rubber tires as idler wheels that have the same overall dimensions as our 42×19mm wheels. This product includes two idler sprockets/hubs, two rubber tires, and mounting hardware consisting of two shoulder bolts, two nuts, and two washers.
They can be used with the included rubber tires as idler wheels that have the same overall dimensions as our 42×19mm wheels.
Dimensions
Hub diameter: 1.38" (35 mm)
Wheel diameter: approx. 1.65" (42 mm)