The dual-quad LED 400A daytime is greater than 400 lumen, but the rub is an amber or red light can not be measured for lumen accurately, like most white lights can. An amber light requires less output to be seen in daylight, and a be-seen lens by design purpose should have diffuse light output. It's true a bright white light is appropriate for the night time part of double duty if night time use is desired. DiNotte's 400A is not effective for seeing with beyond a short distance at night in an urban setting with other light sources nearby. In a rural setting without other lights, the high steady is good for about a 100 feet ahead, and is kind of cool in a yellowed black & white photo kind of way. Now I'm participating in the very thing I dislike about these daytime light discussions, and that is interjecting irrelevant night time experience.

The main difference between the three 400 model mounting option packages is an additional helmet/forehead mount option with the 400L listed at the web store. FYI, I'm sure this helmet/forehead mount is available separate. I have DiNotte's 400 clamps with quick release feet on modern & vintage road bikes, a cruiser, and a mountain bike. Each light has many different size clamps for various tube sizes including an aero tube shape clamp, so no practical mounting limitation for a be-seen light that I've encountered.