Replacement kit for rear derailleur outer casing with Campagnolo 12 and 13-speed inner gear cable. The rear outer gear casing is under a high level of pressure as it leaves the frame and bends into the rear derailleur, overtime a kink can develop at the end of the casing and affect cable shifting. When you need to replace your 12/13-speed inner gear cable, it is often ideal to replace the rear outer casing to get the maximum performance from your Campagnolo 12/13-speed groupset.