I used 2 12" lines to the check valves(2# for disc, 10# for drums) then basically the same for the front, but ran the rear line down the driver's side to the "T" at the rear. I don't know exactly which sizes I used. NAPA now has a handy dandy kiosk with all their brake lines hanging out in the showroom. If the height proportioning valve is not properly adjusted your coach may wobble and wander all over the road. If you have a handling issue the first thing to check (after your tire pressures of course) is the adjustment of these valves. Do this prior to any front end alignment.