Adapter Splined 3/8 Drive

Comes in two sizes, smaller and larger to fit what I need it to (your mileage may very) Splines are curved (don't ask me how I did it, I just did it, it was hard. They're involute-ish maybe(?), I did a lot of measuring, guestimating, draft prints, and trial and error) Prints without supports

Testing to failure I found that: PETG 

• 3x wall loops failed between 125-150 lb/in
• 5x wall loops failed between 150-200 lb/in
• Both exhibited same failure mode, the square-drive slot turned round
• Either torque was high enough that it would indicate much bigger problems than a broken tool if encountered during borescope inspection
• I did not perform test with 100% infill or higher wall loop count