Quote Originally Posted by Roverlord off road spares View Post
You will probably find the genuine ones are a softer material, they flex more and the lip sits nicely on the groove. The aftermarket ones you'll find have a harder feel a more plastic feel. They split and don't go the distance.
Genuine ones aren't expensive so why would you bother with aftermarket ones. A lick of silicon on the lip also helps them stay there. It's quite amazing how something that just sits there can go through mud dirt bush and still hold on.
Why use aftermarket?
Well that's what my axles had on them, so the first attempts were trying to make them stay put.
When I split one, the local independent rover guy only had the aftermarket ones. I'd expect most of his uses are for grease lubed hubs so the fit isn't as important.

It's availability that often dictates choice. But now I have a small stash of originals I should be right for a while.

The aftermarket ones as well as being hard (despite being marked as "PU") enough to split are a loose/sloppy fit on the hub and the lip is not the correct size, distance from the end or uniform the whole way around.