i didnt have to use any sealant on my other L series and the extractors fitted fine, a different pair of extractors that hadnt been cut and shut like these. but those ones have blown out then gasket a number of times so i cant see how they can be flat and still do that. its not like L series have a problem of not having enough clamping on the extractors

pretty sure i'd even put a straight edge over them and seen that the number 4 flange was on a different angle to the rest