Boner I, have used one for several years , It serves two purposes , one, is to help mud ,etc. from entering the top of the air box and two , it supports the rear fender ( mudguard ) in the exact position where you seem to sit when fighting for grip with both feet down . Without it ,the fender will flex quite a bit and will eventually fracture !! I highly recommend one and the cost will perhaps save you a rear fender in the long run !! cheers Geeman