Imperial measurements are circumference, metric are I believe diameter. Remember the RMAS TuTs when they came home had something like 5.5" wires, then they went to what was I believe called steel rope, which look synthetic made ropes, which were half the size and very light, the TUTs were 35t bollard pull. I remember the coloured tabs, used to be company name on the tape, to stop thieving by other operator's.