Well, I'm not a Jagwire fan. The steel wires in the casing run parallel to the length, instead of coiling like classic housing. On a recent ride, that enabled my rear derailleur cable to actually slice through the side of the casing. That disabled the derailleur. I was able to lock it into one gear and finish the very hilly ride shifting just my three chainrings. Yes, I admit quite a bit of fault in the failure: I didn't use proper end caps on the casing, and I didn't lube the vintage derailleur adequately and it became tough to move. I also used the Jag casing in an area requiring a tight bend, and it doesn't like to bend like that. All in all, though, I installed it just as I would have installed classic casing. I replaced the damaged section with vintage spiral casing, and everything works great again. Bike is my 1970 Mondia Special 650b conversion.