I created this to hold 2 sets of Warrior brand nut drivers from Harbor Freight (one set metric and one set SAE).  The holder is meant to be attached to a carabiner and put in my tool bag (with some other ¼" bits and adapters).  The holes in the center piece are meant to use M3 heat set inserts, and then the factory rubber holder gets sandwiched into the 3D print on the respective side.