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° 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 high quality 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.