Caution...
Just a note of caution with these caps!
I had need to fit one of these to a Ford Scorpio that we once owned and for some time after fitting, suffered fuel starvation which would re-occur and took us weeks to eliminate the problem. It was caused like this... each time the cap was removed from the filler neck a tiny sliver of the expanding plastic that protrudes into the neck was shaved off and fell into the neck and found its merry way into the tank where the fuel broke down the oil based plastic until it was a jelly like substance which eventually blocked the fuel filter and a vacuum was created which would stall the vehicle, as soon as the engine was stalled the vacuum would cease, the engine would refuel and the jelly would swim itself around the tank until it found the filter again!