The saddle diameter can be adjusted, and can be fixed in any type of cd tube, PF tube, VE, steel tube, cable, etc. Grooved openings for easy diameter adjustment. It can be firmly fixed with one screw. D8/13/18 has side-prevention and biscatch function. Compatible Diameter: 1.3 - 14.6 inches (32 - 37 cm), Compatible Tube: 1.1 inches (28 mm)