If you own a set of SportCrafters or CycleOps aluminum rollers and you want to turn them into an interval machine, incorporate the SportCrafters OverDrive Drum with ARC Technology and be ready for this spring's town line sprints. ARC Power Modulation Technology was developed by SportCrafters to increase resistance in rollers without external resistance units. These rollers feature high power magnets on the inside of the drum, which are drawn closer to the drum wall as speed increases. The closer to the drum they move, the more the resistance increases. Progressive resistance allows for a more realistic road feel. Additionally, when you are performing intervals, they provide the higher power needed. By doing intervals on rollers rather than on a trainer, you have the added benefit of developing balance, core strength, and stability, while also gaining power. The SportCrafters OverDrive Drum is a machined aluminum 3. 25in drum, with the same lifetime warranty as all of SportCrafters' rollers. It is compatible with all SportCrafters rollers and most CycleOps rollers. The width outside of the end caps is 16. 125in. The width required between the outer rails is 16. 75in. The axle is . 375inch and will fit through a side rail up to 1in thick. It is available in one size.