Material: The bell is made of metal with a smooth surface. This is sustainable. Size: The diameter of the bicycle bell is about 5.8cm. Bicycle bells can also be used to decorate bicycles. Installation: Just use a screwdriver to tighten the screws on the bell-shaped bracket to complete the installation. Very simple and practical. Installation diameter: 21-23 mm. The sound is crisp and loud: the aluminum alloy bicycle bell can emit a crisp and loud sound, which can be heard clearly, making it safer for you and your child to ride. Uses: Bicycle bells can be applied to old-fashioned bicycles, children's bicycles, portable bicycles, etc. It is an essential bicycle accessory for children and adults. Product description Specification:Material: Alloy steel Size: 5.8*2.8cm Installation diameter: 21-23 mm. 90g Package includes:-1 * Bicycle bell