Polycarbonate for improved durability. Fast and Easy installation with universal bracket band clamp combination. Removable front edge for grinding close to wall. Brushes on base make it easier on rough surfaces like grout, ledges and pitted concrete. Complies with OSHA Silica Rule and EPA regulations for point-of-origin dust containment. Fits up to a 5-inch wheel on most 4.5 to 6-inch angle grinders. Fits collars 2.1in down to 1.3in.