I was fed up with the original rubber O-ring that was supposed for mounting the Flux rear light to the bike, so i designed my own one.

I made a mount for a standard round seatpost-diameter of 27.2mm (tried and tested) and 25.4mm (not tried yet).

To fix the light to your seatpost, you simply slide the mounting bracket onto the light from above. It's intended for the light to rest on the seatpost-clamp.

It is designed to be kind of a firm wedge type of fit and it “clamps” nicely to the seatpost. (You may have to tinker with printing offset settings but it should be good to go)

I'm using the 27.2mm version on different bikes on a daily basis (commuting/gravel riding/all-weather) for a few months and it is as good as new and still very secure. It does not rattle and it never came off or even got loose on my rides.

Info on printing:

Supports for the cutout are probably necessary.

I printed mine in matt black PLA and it works perfectly fine and it blends in nicely with other matt black bike parts.

You could print it in PETG for more strength, if you feel anxious ;)