Picked up GM's locking gas cap from my dealer. Because I had complained about the potential dirt and water problems with the capless system they gave it to me for free. In any event I took it home and tried it on my truck. It seemed to fit snugly but when I went to take it off, that was another story. The top seems to get caught on the inside of the gas cap and it can be a struggle to get it off. I guess this was GM's idea of a quick inexpensive fix from complaining customers. I will have to make some modifications on this cap to make it fit properly for removal....