That's the one I am using in the photo above. As I say, on their own they will not compress the mat effectively or even at all but, if you do as I do and use them to store your complete sleep system (mat and bag) then they compress the contents very well.
Looks like this when packed, That is, Downmat 7 (folded in half lenghways and rolled) + minimus (rolled aound the downmat). drybag is a medium size. They should fit into the small version too which will probably give better compression.