I tried using the inner lining that comes with the Jagwire cables but the fit was too tight.. I probably could have gotten it through but I was literally to the point of having to jam it through and it was moving a centimeter at a time. Finally decided it was best to just discard the inner lining, and all worked fine. Guess I'll never know if shifting performance would be better with the liner.. I wish the inner cable routing was the same diameter as it is on the brake side because then you it'd definitely slide through with ease. Sucks to buy the fancy cables, read about how the super duper teflon lining provides superior shifting, only to not be able to use it. I'd probably never notice it one way or the other, but I think it's safe to say that most of us here want to get maximum performance for our dollar, no matter how incremental the performance increase is.