The Moon Ring is a super compact rear light with a 25 lumen output which packs a punch despite it’s small size, but it doesn’t quite have the power or battery life to compete as a dedicated rear light for serious night riding or training.
Mounting the light to the bike is easy with two rubber O-rings provided, in 20-35mm and 35-52mm sizes, so you can strap the light to your helmet, fork, handlebars and other spots on your bike and person, as well as on the seatpost. Having the option of two O-rings also means the mount will work with aero tube profiles.
The light slots into the mount with a reassuring click, but I did have a slight issue keeping it at the perfect angle. You can adjust the beam angle by loosening a screw and moving the light to your ideal angle, but this is done in increments, so I couldn’t always find the perfect position. It’s a small niggle, though.