DRYGRES 4DRILL diamond drill bits are designed for use with electric drills (including cordless drills). Hexagonal connection of drill bits with 13 mm head. Very useful for breaking both very thin and thicker materials. All DRYGRES 4DRILL bits have a wax inside. The wax melts with the use of the drill bit and improves cooling and removal of drilling debris. Revolutions per minute - 1000 min., Maximum drilling length - 40 mm, Number of pieces in a box - 1