After inserting the batteries, happened only once nothing. I thought I might have the batteries been inserted upside down. Tried all directions. Nothing. My husband 'repaired' it then and told me that when inserting the batteries, the light is bridge
For the price I was skeptical! I thought then on a cheap scrap of not even 10 cents value - but does not register! This taillight exceeds my expectations. Extremely bright, light and easy to assemble without tools. The bright light is already perceiv