1. [Easy to Install]- The package comes with two 4mm and 5mm allen wrenches. When installing, use the hex wrench to fix the screw to the bicycle handlebar, and then tighten it to ensure a firm closure. 2. [Handlebar Bike Mirrors]- Bike mirrors are made of acrylic convex mirror, which has a large field of view compared to traditional glass mirrors. The fully adjustable 360¡ã design bicycle rearview mirror can be installed at the end of the handlebar to help you observe all directions of your back for riding. Note: Please remove the protective film(not the label) before using. 3. [Bike Bell]- Bicycle bells is made of aluminum and plastic materials with coating process, which are wear-resistant, anti-rust and waterproof. The sound of bike bell is loud and clear, which makes you r while riding. Bike bell fits most handlebars with a diameter of 7/8 inch(22.2mm). 4. [ Design]- The bicycle mirror has a high-impact nylon frame body and a flexible and durable aluminum fixture. The compact design makes it shockproof, and the folding design makes it avoid obstacles.