My 2006 4Runner has metal valve stems on chrome wheels...its the air pressure sensor type. The metal caps on the valve stems were frozen on....I needed pliers to remove them. In the process I wiped the threads off of 1 stem & completely broke the top off another one. The caps are sturdier than the metal (aluminum) valve stems... The dealer wanted $200 each to repair them (the stems themselves are $150 each) then labor, rebalance each tire, calibrate sensors etc.... The dealer said he has seen many of these caps seize on the stems & after the repair (lucky they were still under warranty) replaced the caps with plastic ones. IF YOU HAVE METAL CAPS I HIGHLY RECOMMEND YOU REMOVE THEM BEFORE ITS TOO LATE!