Thanks Bengt. I'll look for it. I'm talking about the lock cylinder, the part that the key fits into. A new gas cap (incredible price!) comes with the cylinder separate, complete with key. You insert it into the cap and a bit of twisting and turning, it clicks into place. But it must be possible to get it out - I just can't see how. After all, replacing the lock cylinder or barrel is quite normal procedure with house door locks, like when you have lost all your keys you don't have to change the whole lock. See what I mean!