Metric or Imperial Socket Sets
If you’re buying a socket set for someone else as a gift, before you do anything else, find out whether your friend needs a socket set to fit metric (mm) or Imperial (inches) nuts and bolts. If you’re not sure, and unless he/she has an American car or a British Classic Car, buy metric.
Other considerations will be the size of the set: very comprehensive for a professional or a small basic set to stick in the boot for emergencies or something in between for the home mechanic.
A Selection of Socket Sets from Amazon
Socket Sets on eBay