I bought a set of rollers at a 2nd hand sports equipment place for about $65. They came complete with a skid mark on the frame where the last owner left the rollers and headed for the carpet at top speed. I added some casters set horizontally to keep the bike wheels on the rollers. But, I have never been able to get the hang of riding them without setting the rollers in a door frame so I can use my shoulders to prevent disasters.