The light straps on to the seatpost. If you have a large aero post, it's supposed to fit. With enough effort to stretch the rubber far enough, it is possible for a strong man to affix it to the seat post.
Charging is a nightmare because you don't want to take it off because that means you'll have to put it back on and that's going to take a few minutes of twisting and pulling the rubber strap to affix it to your seat post the next morning.
The base of the light begins where the fixture ends, about 1cm aft of the seatpost. The light then protrudes quite far back from the seat post. If you have an aero seat post, it is going to be difficult to get it to stay in the middle. Instead, it will tend to wobble and rest at a slight angle.
The usability of the button is fucking stupid. They have oversimplified the features into one button. The one button is tiny and hidden on either the top or the bottom. To turn the light on, press hold and the top and bottom of the light for three to four seconds. You won't be able to feel the button with gloves on.
The one button also controls the number various of flashing features. It's easy to accidentally switch modes when turning it on. Then you have to cycle through all of the modes to get it back to the mode you had it on before.
Overall, NightRider gets the following grades for this light: Usability ..... F Ergonomics ..... F Form factor ..... F
Agree with prior review. Love the Brightness & multi-functions although I usually stick with only a couple as I ride mostly early am & daytime. 2 Straps so It should allow to be used on a Seat Stay too. I've used on Seat post only of several bikes & have switched straps when a larger / aero shaped post is involved......strap is a bit longer than it needs to be but I have not cut. Does NOT move underway. Well made, easy re-charge. Keeps flashing - short, medium or long (century) rides.....never hurts to remember to shut off at stops even short rest stops
I got this tail light and the Lezyne Strip Drive Pro 300 for myself and my wife, who is a fledgling cyclist. I let her pick which one she wanted. I put them side by side in a dimly lit room and we observed them. I bought the Lezyne because it goes to 300 lumens - this only goes to 260 but the unique design looked really intriguing. She chose this one; it was obviously better in every way. Every single flash is 260 lumens, and the deep wedge shape means that unlike a simple strip of lights or whatever, you have this big surface area that shoots an enormous amount of light out to the sides as well. The Lezyne, on the other hand, has the usual strip configuration and only every 3rd or 4th blink gives you the big 300 lumens. Not bad at all but not as good as this. This thing is also light and compact, and attaches easily with a simple rubber thingy. It turns out that it's reliable, charges quickly and we have not discovered a downside to it. I might get one for myself as well, since I absolutely do not skimp on light when having to constantly deal with large numbers of hostile and/or distracted urban drivers. Brighter is better!