Sportbike Track Gear is having a sale on Spiegler stainless steel brake lines for the Z900 so I decided to give them a try. I bought lines for the front, which I've always found weak on my '17 Z900. I just installed the new lines, and WOW! What a difference. My front brake lever now gives me some feel and feedback. What a concept. The brakes also feel noticeably stronger. I highly recommend this mod. I just ordered a Spiegler line for my rear brake.
Spiegler lines come in different colors. You can separately choose the line color and the fitting color. I went with clear lines and natural aluminum fittings for the front.
I have attached some pics. Apologies for the quality. It was in my garage at night, and the bike is kinda dirty...
If you decide to do this mod yourself, STG has a really useful series of how-to videos (