Exapndable Rubber Drum Wheel was Angled expansion slots through the heavy rubber rim allow the drum to expand when rotated; thereby locking the belt in place. the best way to obtain smooth, highly polished stones. The soft, pliable rubber expands during rotation to grip the sanding or polishing belts.Belts can be quickly changed by stopping the machine, slipping of the old one and sliding on the new. In use, the resilient drum surface flexes to the gemstones contour to quickly remove grinding flats. The convex shaped drum provides the cutting action necessary to remove scratches.Expandable Drum Sander Wheel will expands when the machine is turned on which holds the sandingbelts in place when the machine is running.Sold without belt. Maximum recommended speed is 1800 RPM. CAUTION: Do not run the drum without belts in place as damage to the rubber rim may result.