Put some clear silicone sealant in the joint where the pipe and silencer meet, and you won't need a rubber connector. I think it works better than the rubber anyway. It's easy to get the silicone off when you take the bike apart later as well.
It's not important. The only purpose it has is to keep spooge from spraying all over the place. Silicone sealant works better anyway. Yeah, I'd use it if your bike spooges, but if not, it won't do anything.