Sorry guys got a little busy on the weekend...
The Velour and Pleather look to be cut from the same pattern so I'll just show the velours in a few of these pictures as the pleathers are mounted on my GMP 8.300 D's at the moment.
These new pads will stretch out to fit on any 100mm diameter cup rim, they might stretch a little further but they would not fit on my T50RP's which are 110x100 if I remember, I didn't want to stretch the back out to the point of ripping to try.
From the GMP thread:
Mounted on the GMP 8.3 series.
66mm inner opening length when mounted on a 100mm cup.
Now for the Monoprice 8323 size question, I am using the Velours in these pictures.
Monoprice 8323 - Pearstone Deluxe (Left) vs HM5 (Right)
The Monoprice cup does not stretch the pad in any way so here are unmounted pad measurements.
*The inner depth is the same as the Pleather pad which is 27.5mm*
Back 105mm length.
Back 83mm width.
Pleather = More Bass / Velour = Less Bass
Any other questions just ask.