When I purchased this RT the rubber brake lines were already almost twenty years old. There were no obvious signs of age such as cracking or leaks, but the brake lever was spongy, and even after flushing out the old fluid, wasn't as firm as it should be. Several kits are out there for replacement lines featuring teflon tubes covered by a stainless steel braid, which in turn is covered with a clear or colored plastic coating to prevent abrasion to adjacent components. They boiled down to two variations: The first kind were a one-to-one replacement for the BMW factory lines, and left the steel brake lines intact. The second kind used two identical lines that extended from the master cylinder on the handlebar to each caliper. I wasn't thrilled with the one-to-one kits as they left the hoop of steel brake line that connects the two wheel calipers intact. That hoop extends up and over the front wheel, then down to the calipers, and is infamous for trapping air when the brake system is opened. I didn't like the idea of a double long banjo bolt at the master cylinder either, but it was necessary if the second option of double brake line was used. I knew that "T" and "Y" hydraulic fittings were available, but was unable to find a kit that used one to provide the best option: A single line at the master cylinder going to a centrally mounted "T" and lines extending from there to each caliper. I'd been making brake lines for years, and figured it was just a matter of figuring out the proper fittings to make this one too. After looking at the available options I settled on Earl's Performance Speed-Flex hose and Speed-Seal fittings. The hose is rated to 2000 PSI and the fittings were available in both stainless and zinc plated steel, plenty strong enough for a manually operated motorcycle brake. I purposely stayed away from aluminum fittings. There's an engineering property of material called a fatigue limit, defined as the number of times a cyclic load can be applied before a component breaks. With some materials such as aluminum, the number of cycles varies inversely with the size of the load. But no matter how small the load, the component always fails. With other materials such as steel, there is a load below which, no matter how many loading cycles are applied, the component will not fail. Since brake lines live in a high vibration environment, and I very much like my brake line fittings not to fail, I chose steel components. And since I'm the cheapest thing on a BMW motorcycle, I also chose the zinc plated versions.