They are 2 different sizes..
The cork or `rubberized cork' ones suit the early covers, 850-998-1098(their middle bit sticks outwards and the gasket face is flat).
The red silicone rubber ones suit the later covers 998 Clubby and Cooper S, these are dished in the middle. I have never had one of these leak from the gasket. But they will leak around the bolt if you don't use the right cupped washer and square rubber seal ring.
_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
