I ordered the medium and my hands are about 17cm long wrist to middle finger tip. Usually I get everything in the smallest size possible, but due to other peoples comments I got a medium. It's a little big, but not by much, for all I know the small could have been too tight. It doesn't really matter anyway, these are for holding bike handles when it's cold, not for surgery. Can just about operate a bike lock with these on, that's about the extent of the dexterity you retain.