I designed this model to mount the Specialized Flux rear light to the di2 junction box on the seatpost of my Tarmac SL7.

I fixed the mount to the bike using one of the srews that holds the junction box, and double sided tape to be secure.

The light clips into the mount from the top. It's nice and tidy, tucked away under the saddle. I also designed a little “squeeze to unlock” type of snap-closure that prevents the light from getting loose.

There's even a little TPU insert, so the light doesn't rattle and is firmly locked in.

The snap-lock and the insert are supposed to be glued in place.

I printed mine in matt black PLA because it blends in almost seamlessly with the seatpost.