The Lessmann Conical Knot Brushes with left hand twisted knots to increase stability. The special shape of the conical brushes enables the user to work in hard to reach places. They have been designed for heavy-duty use, for the preparing of metal surfaces before painting, and the removal of slag, rust, scale, or concrete waste. Diameter. 115mm. Width. 10mm. Bore. M14. Wire Gauge.0.35. Wire Type. Steel. Max R.P.M. 12,500.