Check the listing for details. Rotary tool, corner guide and cutter attachment, Cleans out 90° inside corners,. Condition: New. Listed at 40.00 USD. This attachment is designed to clean out 90 degree corners (arms) or vertex that may have a radius or other undesirable features using popular name brand rotary hobby powered tools. The included 1/8"(.125) diameter double ended carbide cutter (USA made) will cut wood, plastics and most metals. The guide housing is machined aluminum and the guide nut is a tough plastic. To use the tool, hold the power tool with attachment adjusted and mounted, 45 degrees relative to the workpiece. The flat machined area of the metal guide should always be perpendicular to the vertex (directly 180 degrees opposite the area being machined). Setting the cutter length will be shown in above picture with the red aligning arrow. Exposing more of the cutter will produce an undercut or groove. This could be useful welding or sealing groove. A radiused, flat or spherical cutter can also be used, as long as the cutting end is less than .125 diameter, the inside diameter of the bearing.