Four LEDs in a box that’s well sealed and runs on a couple of N cells doesn’t sound like a fantastic light, but to be honest it’s very good.
The two main rearward-facing LEDs do a good job of keeping rear visibility high, and the other two LEDs face outwards to the side at 45-degree angles but aren’t shrouded. The rear lens lights up nice and bright making all around visibility good. The mounting is simple and accomplished by an O-ring fitting to one side, wrapping around your seatpost, and then looping over the other side. This means it can fit almost anywhere, and if you use the right length O-ring it’s secure, too.