... Skin-friction force:2.5,2.8,3.0,3.2,4.0. Diameter:2.0-12.7mm. Matt ball1. Skin-friction force ... :2.5,2.8,3.0,3.2,4.0.2. Diameter:2.0-12.7mm.3. The matt ball widely ... .00.0450.038.0-10.518.0-20.50.13160.300.752.00.0450.0310.0-14.016.0-18.00.12.0-3.0 grinding steel ...