This question is regarding the supply lines from brake resivoir to the low pressure end of the master cylinders. On my rv8, I used the nylon t fitting at resivoir and then the nylon type supply lines down to the masters where the connection were with a brass fitting with collar. Has been working fine for last year. While bleeding my lines on a Citabria I notice that my A&p fixed my leaking brakes with simple Black barbed T's and what looks to be vinly tubing (clear flex tube). Simple zip ties on each end of the vinyl supply line to the barb fittings. Now since this is a certified aircraft, How is this legal for starters? Second, will vinyl hold up to the brake fluid? It seems weird to me but then why wouldnt vinyl tubing work?