What size cable insert do I need?
To pick the right cable insert you need to know the outer diameter of your cable. Then you need to pick the insert that is most suitable for your cable size. The inserts go up in increments of 1 mm.
For example the KT 4 insert is suitable for a cable size of 4-5mm, the KT 5 insert is suitable for a cable of 5-6mm, and so on.
More information on the KT inserts can be found here.