Usage Tips:4 Modes bike back light: comes with 4 modes completed within 1 switch, including full brightness, half brightness, fast flashing slow flashing, which can be seen from a far distance, you can be easily noticed by others in the dark, increasing the visibility safety USB rechargeable design: built in 330 mAh rechargeable lithium battery a USB pt design, you can use any device with a USB interface to recharge the bike tail light; there is a USB cable attached to each bike tail light, allowing you to charge from your computer, power bank any device with the USB pt Easy to use: the silicone mount strap of the bike back light has 4 openings, easy to install on the hlebars seat posts, bike tail light tightly fits around most size hlebars seat posts, you don't need other tool to install it Wide range of applications: not only can these rear bike lights provide illumination f most bikes, such as racing bikes, mountain bikes so on, but also they are suitable f attaching to most bike frame, seat post, hlebars helmet, hook onto your belt, running gear, reflective vest, backpack, dog collar, harness so on USB Rechargeable Bike Bicycle Cycling 4 Modes 5 LED Front Rear Light Lamp Technical : Brightness: 15 lumens Mounting Positioning: post bicycle seat Bulb Type: Led Suitable Pipe Diameter: 12-32mm Please long press f on or off. Colour:red Material:ABSandPC Size:7 x 2 x 1.7cm Package Contents: 2 lights 2 straps 2 USB cables Note: As the taillight is , maybe have some low battery case. please charge befe using. If this makes some problems , we feel really sry. Only the above package content, other products are not included. Note: Light different displays may cause the col of the item in the picture a little different from the real thing. The measurement allowed err is 1-3cm.