Great to see another finger getting stuffed into a cock cant get enough of watching other people stuff there finger or someone else's finger in there cock, keep it up .i love my wife jaming her finger's in my cock any time.
As a plug diameter I would just take the diameter of the largest dilator that I can introduce. After about 2 to three weeks, the plug will fall out and you can introduce the next largest. As low a plug has been found with an olive shape and a slender neck, of course, with longitudinal bore. The plug slides in and then you can no longer feel in because it fits perfectly into the urethra navicular fossa.
I found a similar plug 10mm
For two days not a drop fell