Utilize to tightly secure Scotch-Brite Stars with 1/4-20 internal threads for a safe performance. With the 3M Star Mandrel, you can use your die grinder with the uniquely shaped Scotch-Brite Stars to clean, polish, and lightly deburr the inside diameters of pipe and tubing. The 3M Star Mandrel is 3 in (7.62 cm) in L with a shank size of 1/4 in (0.64 cm). Thread size is 1/4-20 EXT. It will run safely at a maximum RPM of 24100.