Only one casing?
There are two cables but only one outer casing, does that mean one cable has to go uncovered? Seems a bit strange...
Hi, it is one length of outer casing which can be cut to the lengths required so the one length should be enough cable to cover front and back cables where they need covering.
Use a proper pair of cable cutters to do this job - if the plastic pushes into the barrel of the cable, feeding a length of inner cable through should be sufficient to clear it.
Hope this helps.