Wire end sleeve sizes and insulation?

Hi there,
I've bought Hicon banana connectors and it says 4mm cables and max 4.2 mm cables.
But when I check wtb's wire end sleeves, it says 3.2 mm outside diameter even though it is 4 mm based on the product's description.
Should I instead then get the 6mm for 6mm cables which has in it's product description a diameter of 4mm though?
Connector

https://m.thomann.de...=0&search=1579546700

4mm

https://www.dienadel...-4-00qmm/a-353631157

6mm

https://www.dienadel...-6-00qmm/a-353631158

Isolation

https://www.dienadel...-6-00qmm/a-353631199
IT looks like though that the 6mm is the right choice for my Hicon Banana for my 4mm cable right?
And the question is with or without isolation?