Lt95 110 gearbox oil leaks

I have the seat base and floor out of my 110 at the moment and just trying to resolve some oil leaks. It currently has a major oil leak from the gear selector seal. The one that currently is on there is made of a felt like substance and had enough play you could lift the gear lever up maybe 3mm. I today bought a new seal appears to be a latex type of material to replace the old seal. Is it normal for the internal diameter to be significantly smaller than the one currently on there and also smaller than that supplied with the genuine gasket set which appears to be cork? With the 3 bolts that clamp down against the seal it would appear not much clamping pressure would be applied due to the bolts having a spacer at the top of the thread.
Let me know if you need some photos to explain it better.
Here is the range of seals, each is different to the other and they are all meant for the lt90
Currently fitted, Genuine Land Rover, Latex rubber seal