This adapter is a lower profile mounting solution for the “Moon” branded rear bike light. Unfortunately, every brand seems to have their own standard but I made this for a friend and thought it could be useful to others as well. 

It made it super low profile so it does not get knocked off when folding the Brompton with the Advanced Roller Rack. It replaces the reflector on the rack. As you probably know, that rack does not leave a lot of room around that area with the standard roller wheels.

I designed this to be printed with 64D TPU, if you print in another material, the retaining tab will be a weak point.