A simple 'click' of the lens will power up 2 LEDs that pump out up to 20 lumens of beautiful, bright light that is even visible from the side of your bike for cross traffic. The silicone mounting strap makes it easy to install/remove and works on pretty much any handlebar or bike frame from 15-35mm. Ingress protection rating or 'IP Rating' is a techy way to describe the level of water and dust-proofness a product has. This light meets the IP-65 Standard, which means it is totally protected against dust/grit and fully resists strong jets of water from all directions. Two CR2032 coin cell batteries are included and are super-easy to replace.