[Auto/Manual Mode]Automatically turn on/off depending on the light intensity, and motion, Automatically switch to sleep mode to save power, Press the button turn the cycling taillight on, then press button twice to change the different mode(auto sign turn on green light,auto mode open). [Battery Life]Built-in 4000mAh Polymer Lithium battery comes with a USB cord that charges from your computer, wall charger, power bank or any other device with a USB port. After charging for about 2 hours, the tail light can work for 10-30 hours in different modes. [Mount System]Saddle mounting bracket and adjustable silicone strap provided, make the bicycle rear light flexible to quick install or detatch on bicycles. Very convenient to remove out from the bracket for recharging. [Brake Light]Super bright light promptly provide warning people behind. [Waterproof and dustproof]Against splashing water from any angle. Riding in the rain never be a problem again. Type: Highly Brightness Bike Taillights Light Color: Red Light Modes: Constant / Flash (6 totally) colour: black Material: Aluminum Alloy Package Contents: 1 x Bicycle tail light 1 x USB charging cable 1 x English manual Only the above package content, other products are not included. Note: Light 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.