Chain and Sproket

[Grahamm]

X is superior to O in terms of sealing ability but the biggest difference you'll see is down to how you look after your chain (and how you ride). A regularly lubed (scotoiled?) O-ring that only gets ridden in the dry will last longer than an X-ring ridden in all weather.

Thanks for the info. Given that the bike's 5 years old and has done 26k on a standard O Ring with Scotoiler, I think spending the extra dosh probably isn't worth it.