On unmounted flap wheels, the flaps made of coated abrasive are arranged radially around the tool axis in a fan-type structure. Their flexibility enables them to adapt perfectly to the contours of the workpiece. The abrasive grain is embedded in the sturdy, flexible cloth backing material by means of a resinoid bond. In ISO 5429, unmounted flap wheels are designated as "flap wheels". The ideal tool for use on angle grinders in assembly shop operations. For general applications from coarse to fine grinding.