what size? Uh...I dunno... I guess all sizes?

I try to have every size I need...I have a full set of standard and metric allens up to about 3/8 inch in size (I have the regular allen wrenches, but a lot of people like the allen drivers.)...also 2 different sizes of screwdrivers- both flathead and phillips... a nutdriver set up to 3/8...and a 4 inch crescent wrench... also a few different sizes of pliers...

then in my soldering/electrical box, there's a full set of tools for that type of work...

more tools in the flight box for those applications...