Compliant wheels are not intended for moving robots, but moving objects. Compliant wheels give way to allow rigid objects to be manipulated easily. A line of multiple wheels on a driven hex shaft creates a very effective roller that ignores variations in the objects being driven. This makes for high-performance intakes and internal conveyors. The wheels are sized for an interference fit and tend to stay in place on a shaft, though a shaft collar may be used to make absolutely sure the wheels stay clear of other mechanisms or maintain consistent spacing.
 
The hex bore versions of this wheel are undersized, and are intended to be an interference fit on their respective hex shafts. This interference fit allows for effective torque transfer from the hex shaft to the wheel, as well as allowing the wheel to remain in place along the shaft without the need for spacers or collar clamps:
 
Different durometer ratings give each wheel unique characteristics. Green wheels (35A durometer) are the softest and most compliant around objects, while orange (40A), maroon (45A), and blue (50A) wheels are increasingly firm. The increased firmness also allows the latter wheels to carry a higher RPM rating. Check out the downloads tab for a chart showing wheels and their maximum RPM.