This is a TBS ND filter (aka "JelloGuard") holder for the GoPro Hero 5/6/7 Black desgined by Lucky7FPV.
Unfortunately he deleted his account on Thingiverse, so the original file isn't available anymore.
However, it's the best TBS ND filter holder I could find so far, so I thought I'd redistribute it.
The picture is also taken from Lucky7FPV's original upload.
Print in TPU.