Morris Minor door seal
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So you fit the cheap seal and when the aircraft gets to it's annual check you risk paying the going rate to have the seal replaced with the correct item.
Do it right and do it once!
You misunderstand, I was just making the point that a non-critical item is easy to come by and cheap, but you can't use it 'cos it ain't approved. The same stuff duly approved will be around 100* the price.