The CatEye™ Solar Cycling Tail Light automatically goes off when its dark and there is movement, so you don't need to worry about turning it on.

• Light comes on automatically when it gets dark and there is motion detected.
    - High-visibility flashing mode.
• Light: 5mm Red LED x1.
    - Battery: capacitor: Solar recharge.
    - Life: about 5 hours in flashing mode.
    - Charges in 2 hours with good weather conditions.  
• Measures: 58.1 x 40 x 31.5 mm.
    - Weight: about 44 grams.
• Imported.