The bottom diameter of the bracket is 2-1/2 inches (inner diameter), regardless of the shape of the rod, it can be sliding fit on the 2-3/8 inch tenon. The outer diameter of the arm is 2-3/8 inches, and any fixture with standard 2-3/8 inch sliding pads can be fixed on it. Three fixing screws are provided for fixing the bracket to the rod. 4" round rod bracket, carbon steel, bright copper/base: 6 screw holes 1 for 3/8" -16/tenon: 1 x horizontal tenon, 90D, OD60x HT 10