Went to change trans oil on the Jetta, and I need a 17mm Allen for the job. I see cheapo 1/2" drives on Amazon, but for 2x the price I could get several other sizes too. Any reason to buy an assortment, or should I go for just the size I need? I have a 7mm for brakes already (and a couple more around that size). I don't what other large sizes I might have some future use for.