I checked the DCS manual and a couple of other place for you about the size, but not specified. I have used them a lot and I am reasonably sure they are 4mm. Here is a general statement from a manufacturer
"The 4mm version accounts for more than 94% of the total usage. In fact, when someone uses the term “banana plug” or “banana jack”, they are almost certainly referring to the 4mm version. The 3mm and 2mm variations are both called “mini-bananas”, but they cannot be used interchangeably."
I looked at 2 and 4 mm on my ruler and I feel confident they are not mini banana. Not Chiquita anyhow!
Dont buy green ones if you plan to eat them today,
Cheers,
Mike