After debating on which tail light to buy, I chose the Mars 4.0. I see many lights out there but this one is by far one of the brightest. Lets just say if you had to you could attach it to the front in an emergency and it would provide enough light to creep home with at night. The only thing I'm not to keen on is that the light will slide out from the bracket however it tends to not lock in the best so I'm afraid I might lose the light. Pros is 20 hours on blinking mode, 2 on constant.