on my S2 I measured 0.65 inch overall height and 0.45 inch high hex portion.
those are not guaranteed exact, I am sure someone will correct me and tell me I am off a ten thousanth of an inch. I just measured them on the car from the top of the copper washer/ bottom of the nut to the top of the dome and top of the hex
mine are original to this car.
hope that helps
Bob