The people at SportCrafters know you don't always want a harder workout, you just want to roll for longer distances. That's why it designed its High Inertia Drum for long workouts, baseline testing, and drills. The High Inertia Drum replaces the middle roller on your existing SportCrafters Cadence or OverDrive Pro Rollers. It's also compatible with your CycleOps aluminum rollers. It allows your bike to coast for longer periods of time without losing momentum. This momentum assists in clipping into pedals or for performing one legged drills. The drum is machined double wall aluminum, which adds more mass and therefore more inertia to the rollers. The 4. 25in diameter drum is compatible with existing rollers that have a distance of at least 2. 25in between the drum axle and the floor. It is recommended that the rollers be used only on hard surfaces. The SportCrafters High Inertia Drum is available in one size and its width from the outside of the end caps is 16. 125in.