Plastic, nylon class 6/6, spec l-p-410; 3.094 in. Outside dia; 0.625 in. Inside diameter and counter sunk to 1.250 in. At 30 deg; 0.750 in. Thk; item has four mounting holes drilled through at 0.188 in. Diameter and counter sunk to 0.438 in. Dia; counter sink of mounting holes being 0.219 in. Deep