The rear-view mirror frame 1 inch (approximately 2.5 cm) ball holder base can accommodate mirror rods with a diameter of 0.39 inches (approximately 1.9 cm) to 0.63 inches (approximately 1.6 cm). The circular rail adapter for motorcycle rearview mirror frames and mini handlebars is equipped with three sizes of rubber ring inserts to provide a tight fit and protect the mounting . Rubber ring pad diameter: 0.5 inch / 0.87 inch / 1 inch. The aluminum alloy mounting base uses rubber inserts and locks to prevent high vibration from loosening. It is used to install to the rearview mirror frame and the motorcycle and bicycle mini handles and other circular rails within the specified size. This 2.54 cm ball seat is made of 6061-T6 aluminum alloy, which is and reliable in harsh environments. The ball adopts TPU molding design, which has anti-slip performance. The 1-inch (about 2.5 cm) tee base is compatible with RAM mounting, dual socket arms and other mobile phone holders with 1-inch (about 2.5 cm) tee systems. Suitable for bicycles, motorcycles, mountain bikes, electric scooters, ATVs, etc. Colour: black Material: aluminum alloy + plastic Package Contents: 1 * Navigation mounting bracket Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.