just to clarify, yes mine are 21 mm. dont measure the taper at the top off the ball joint, push the rubber down and measure the bottom. the top of mine are 17.48mm and the bottom are 21.57 mm
used one of these
also if your car has the xenon lights (shine a bright white colour) then they are 21mm.
if tit has nornal bulbs then they are 18mm...
hope this helps people in the future...................Go to the full post