With virtually no leyway on size you probably want a full set of metric, might get away with 4mm and 8mm by using 5/32" and 5/16"
I started with a set of 1/32" increment imperial but now that I tend to do more metric have almost the full set of those with just a couple in the 20s missing.(15/16 does for 24mm ) I also have 5C to ER32 adaptor so can hold most things.