Can someone tell me the size of the factory lug nut? Someone stole one of mine in the parking lot last night. I think it's 12 x 1.25? Thanks!

 

Keep it simple, take one off, take it to the parts store and try it on the studs they have on display there. That way you won't be wrong by taking someone's best guess. They cost about $2 at Wal-Mart and you have different styles to chose from, plus you might want to consider getting some locks if stealing is a problem in your area.

 

12 x 1.25 is the correct thread pitch.

Edit: And I know this for a fact - just had to buy some myself.