Binocular Tripod Adapter

The slightly smaller 1/4" inch hole allows for a bolt with threadless shank (about 6mm of shank). Screw it through and it shouldn't unscrew but still rotate freely.

The 3/8" hole is slightly larger and surrounding walls/space have been filled in: I screwed in a 3/8" to 1/4" adapter that came with other photo accessories (a little bit of heat helped it go right in).

Binoculars on display are the Vortex Diamondback HD 10x50. There was bending with 20% infill, so I upped it to 70% and gyroid with minimum 3 wall perimeters for an extra bit of stability. 

Added a 7mm hole for a more ‘perfect’ fit for those bolts threaded all the way.

Slightly smaller 1/4" and larger 3/8" holes. Filled in base.