These gray (medium grit) polishers work especially well on platinum. Uniform abrasive distribution allows them to produce smooth, even surface finishes. Moderately hard yet flexible silicone rubber impregnated with aluminum oxide conforms slightly to surfaces. Will hold their edge due to slow breakdown rate.  Applications include removing tool marks, smoothing parting lines and removing casting scale.  Measure 3/16″x5/8″.  Max operation speed 10,000rpm.