5.5, 5.75 and 6mm wrench

thingiverse

Simple little wrenches make quick work of spots pliers can't reach. They might not handle heavy torque, but they get the job done with a quick tighten. For M3 screw/nut combinations, I've found that 5.5mm is often too tight, while a 6mm fits loosely, so a 5.75mm size works perfectly.