I think the cylinder referred to is the metering cylinder
in the drum of the measure, not the cylindrical powder hopper on top.
My Uniflow (older) came with two drums and a large enough hopper, like this one
. One drum with small cylinder bore measures small pistol charges (small bore through the center) while the other (larger cylinder bore) is for larger charge capacity cases.
The hoppers do look smaller on the new small cylinder units. You could call RCBS and ask if the hopper for their Quick Change measure
(the one they now cell that comes with more than one cylinder size) would fit your measure?