With unmounted flap wheels, coated abrasive flaps are arranged radially around the core in a fan-like structure. The flexible flaps perfectly adapt to surface contours. The abrasive grain is embedded in the sturdy, flexible cloth backing material with a resinoid bond. In ISO 5429, unmounted flap wheels are designated as "flap wheels." The ideal flap wheel for use on angle grinders in assembly shop operations. For universal applications from coarse to fine grinding.