Dear All, Apologies if this is a daft question (bear in mind I'm a grieving Welshman!!). I've just noticed that the clear plastic disc which was previously sited between the rear cassette and spokes on my Bianchi is missing after it was returned from my LBS following a service. Does this disc serve any important purpose (ie. stopping debris enter the gearing) or is it OK to ride without it? Aesthetically I have to say the bike looks better without, but I don't want a knackered derailleur in 6 months time!