Your not just limited to 4x100 wheels either as they make alot of adapters to fit different wheels, you just have to do some research first to make sure your offsets are right so you don't run into clearance issues. As far as overall diameter I'd say for an MK1 that 15's are perfect and go no larger than 16's...too big a wheel just doesn't look right on them, some 14's and even 13's can look right with the right wheel/stance
