Yes, I agree with you TT that FastLane is difficult to understand on this part.
Select your Year and Model and then go to "Fuel Delivery".
You'll see 4mm braided hose, 160mm looping return line, and 200mm looping return line. I didn't know what size hose it was, or I might have chosen the 4mm braided hose - assuming the price is per meter.
Instead, I had to choose between the 160mm and 200mm looping return lines. Knowing that there are 5-cyl and 6-cyl diesels out there, I chose the 200mm return line thinking that on a 5-cyl there would be more space between the larger cylinders.
That was the correct choice for my '82 300D. So, I got five or six of these pre-cut 200mm looping return lines. This replaced all the between-injector return lines, and I cut one short to use as the "stub" on the last cylinder that has the plug.
I couldn't replace the length of return hose between the fuel filter and the first injector, but it wasn't leaking. I have some uncut braided hose on the way to take care of that.
Hope this helps.