by the Foot. 6mm is what you need most of. They sell it in 5ft lengths i think. Got ten feet I of the 6mm 5ft of 3mm and 5ft of 10mm. I got the 10mm because I have a RHD and wanted to change the break booster lines. The 4ply lines that z1 and Coz sells are a bit expensive for vacuum lines. I can see getting that for coolant lines which I did and coolant is 8mm.
"torque gets you off the line...& hp gets you over the line." - TTKeeper