All newer Import and Domestic cars/trucks are metric and 10mm can take apart 1/2 of the fasteners on a car so unless you are working on something else 10mm will rule this thread.

So... what is your most used socket? For me it is 9/16.
9/16 is 3/8 drive territory for me.



10, 12, or 14mm are prob used about the same and used the most