.............It's a push through type using inserts in a body.
Left is the nylon 'push rod', stem sized .575". Then the body, and the 2 inserts. One is .576" and the other .577".
The body is 2" long and designed to sit over something to allow the Minie' (or whatever) to fall into a container. The inserts are .750" OD and 1.5" long with a .590" OD leade that's .750" long. There is a short 1/4" taper into the .375" wide sizer restriction followed by a 1/4" relief on the bottom.
The body with an insert installed. I sized a couple dozen Minie' boolits with it both lubed and unlubed before I shipped it. It didn't seem to make much difference in the operation if lubed or not. It turned out well
...............Buckshot