Just a note - it's not for 21mm it's 19mm - which is ok I can buy another deep socket. Here's the real problem: It fits my F-150's threads and has a glans mating surface, but the glans mating surface is MUCH smaller in diameter than my factory nuts. It sits much lower in the rim and I feel like the amount of "grips" it gets on the rim is very small - almost dangerous. One final reminder, you MUST use a deep socket to install these nuts or you will damage them. I wish there was more technical information above so I can make a more informed decision before purchasing. I'll try to return them and take a stronger set of backlash.