Looking at the "AR4 2D Drawings" of the J2 Arm there seems to be 2 holes shown on the side of the arm, each 3.3mm diameter x 10mm deep, but the same holes are not on the printable STL. Are the two holes necessary and if so shud they be threaded to 4mm?
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The holes on the side were originally inteded to secure some of the cables but are no longer used. I apologize those 2d drawings are out of date.