GoPro Knuckles by suatbatu on Thingiverse: https://www.thingiverse.com/thing:487964

Summary:
NEW REPAIRED STL HAS BEEN UPLOADED  A holder a bit different then the others...Feels comfy, easy to handle in action (while running, skiing,skating, diving, skydiving etc.)Please don't punch someone with it. (I tested it for you, it does what a brass knuckles does, perfectly)Some countries, its illegal to carry or have brass knuckles, so know your region's laws.For the bolts, nuts and holder design, this guy has it.http://www.thingiverse.com/thing:163883/#instructions  Check my other designGoPro Frame for Backpac Or Touchscreen (Hero3/3+)http://www.thingiverse.com/thing:888729