Lug nuts on vehicle are 2 piece design with a decorative cap that extends over the physical lug nut. over time, corrosion builds between the lug nut and decorative cap causing lug nut cap to swell. eventually, the swelling is so severe that the factory lug wrench will no longer fit over the lug nut. this is a safety concern due to not being able to remove lug nuts in the event of a flat tire. vehicle is equipped with 21mm lug nuts that swell to 21.65-21.89 or greater. this only occurs on north american-produced rx 350 vehicles. japanese-production vehicles have a one-piece style lug nut that does not corrode like the two-piece style.