A 1/4” (quarter inch) drive 5.5mm Hex (6 Point) Socket
5.5mm is the usual size required for M3 (3mm) sized nuts and bolts, of course other sizes exist but most commonly it’s 5.5mm you want (across the flats).
These are sourced from China from finest quality Chinesium Vanadium, which may or may not have a Chrome content :-)
Good for what ails you, if tightening M3 nuts is what ails you.
All of our products are shipped from Christchurch, New Zealand using CourierPost for NZ, and Airmail for international.