I mostly use screws for metal and plastic, so I use metric hex as well. Therein lies one disadvantage of the metric system: M3 is often too large, M2 is too sma

I mostly use screws for metal and plastic, so I use metric hex as well. Therein lies one disadvantage of the metric system: M3 is often too large, M2 is too small, and M2.5 is not super common. I use 2.5, so it’s only a minor annoyance.