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". For aggressive grinding with maximum stock removal rate on hard materials which do not conduct heat well. Consistently high performance due to self-sharpening ceramic oxide grain. Active grinding additives in the coating substantially improve the stock removal rate, prevent clogging and result in cooler grinding.