Habras Discs provide the convenience of a pre-charged abrasive but do not generate the heat associated with rubber wheels. Embedded cubitron mineral abrasive is much harder than most metal. Removes oxides and polish without using compounds. Ideal for cleaning metal work and hard-to-reach areas. Ideal speed: 10,000 rpm. Discs are 19mm dia. and mounting 4 discs together is recommended for best performance.