BACK-UP PAD (6") Mandrel For Drill ( JV-541)For Janvil HTV backed polishing Disks. Durable design allows for high speed, fast result, polishing. Smooth Mandrel. Fits Any 3/8 Drill Chuck (3600 Rpm Max). Janvil HTV back-up pads are specially designed to hold the polishing disk tight and to absorb excess vibrations. Damage will occur to the glass if any other back-up pad are used with the Janvil Polishing disks.