This tool is used to center and true up those small pieces of stock that are too short to fully insert into your chuck. You loosely chuck your stock. Gently bring the tool post in to lightly touch the stock while you are spinning the chuck by HAND. The roller will bump the high spots and quickly true up the stock to cut or face. Be sure to TIGHTEN the work in place before cutting.There are bearings on each end so you can turn the tool post 90 degrees and use it on stock to be turned or faced. This tool is approximately 4" inches long and made of 1/2" x 1/2" square stock. It should fit any tool post that can hold a 1/2" square tool bit. The roller bearings have a 1/4" bore, are 9/32" wide, and are 3/4" in diameter. There is a stainless steel washer spacing the bearing off the bar. The bearings are held in place with a stainless steel 1/4-20 button head screw ground to length.