I bought a couple extra 10. I bought another 1/2 deep a while back, the cupboard was kinds bare and I found myself loo0king a little harder for one than I should have. Along the same line bought 2 new razor knioves last week and can tell it makes a difference in how easy it is to find one and as soon as I do that a could others show back up. I need tpo do a couple more 1/2 combo and see if some come home to roost.
I bought 2 new 5/16 nut drivers a while back, lost one the second day, I am still one ahead. But,,, 10MM sockets are widely used, even different styles which help with duplication are useful.