This roller upgrade is a single drum that allows you to add quality resistance to SportCrafters and bi-fold CycleOps rollers. Other rollers can be retrofit as long as you have at least 16-3/4 inches of available width between your existing rails (the difference can be made up with washers), and no greater than 18-1/2 inches wide on the outside of the rails (to allow for 1/2 inch of exposed axle to be able to install a nut), and the axle hole is either 3/8 inch or can be opened up to 3/8 inch with a drill (and you're willing to do that).
SportCrafters uses patent-pending technology that employs dynamically mounted high power magnets inside a roller drum to deliver reliable, consistent progressive resistance. Because the resistance unit is inside the drum, there is no external parts, no fluid and no excessive noise.
The resistance has a realistic power curve that allows recovery spin - most likely in the small chainring. Switch to the large ring and a middle cog in the back for base and aerobic power training. At high speeds the resistance really increases so you can even do low cadence power work or 800 watt intervals. Try doing that on a regular set of rollers.
SportCrafters rollers are 100% handmade made in the USA and the actual manufacturer of some other quality brands. The aluminum drum is spin balanced with a tolerance of less than .001" out of round.
The drum should be installed at the rear most position on the roller. To enable the progressive resistance mechanism, install with the red cap on the right. To disable the progressive resistance, and use the roller for easier spinning at higher speeds, simply reverse the drum and install with the red cap on the left.