1-1/4″ in diameter and 1/4″ wide. Very fine wire measuring .006″. These will remove solder and polish up the brass. So far I have seen no scratching. Maximum RPM rating is 12,500. Nicely balanced and fits the 1/8″ collet on your motor tool. As with any wire brush or wheel, always use safety glasses when using. I have not experienced any wires being throw out yet, but I am sure that will happen. These should outlast those tiny Dremel brushes 100:1. Of course that is IMO only, but the quality of this brush is top shelf. wire wheel and mandrel is $15.95.