05 YAMAHA YZF-R6: Galfer Rear Brake Line Kit (Standard) Stainless steel brake lines are typically the first brake upgrade you should make. Stock rubber lines will break down and expand, causing a spongy brake feel or worse. Steel lines eliminate expansion which results in consistent feel and performance. Aftermarket stainless steel brake lines may look similar, but they are not the same! Every Galfer stainless steel line is made with only DuPont&trade; virgin-grade PTFE inner core, 64-strand braid and Galfer fittings are probably the most expensive, but h Rear brake line kit (front lines sold separately).