it is a very thin layer of Poron attached to the neoprene. Also to consider is there are different thicknesses of the neoprene. Could make difference to concussions.
Used mostly CCM for the past 10 years, closer is always a bit of a problem.
Best from the past was TPS by Wilcox. now working with Kenesky.
Currently Ultrasonic. Very comfortable, easy closer, deep pocket.
also a 906 pro owner. Very strong and well made, but old school materials make it heavier that the CCM/Bauer masks.
Look on their website if you want more model/material info.