Simson Ruby-3 rear light The Ruby-3 rear light is designed to keep you visible in the dark. The lamp works on three LED lights that provide a bright red light. The product is splash-proof and works on two AA batteries. These are not included. Specifications: Color: red, black Material: plastic Dimensions rear light: 7.5 x 3.5 x 3 cm (L x W x D) Dimensions holder: 3.5 x 4.5 cm (L x W) Batteries required: yes, 2 AA batteries Batteries included: no Clamp diameter: 20 to 25 mm Mounting position: seat post Type of lighting: LED