The cover itself is about 1mm thick, made of a smooth leather with a natural finish. My large moleskine notebook slid into the cover and fit tightly. Over the last week it has "relaxed" a bit, so it doesn’t gap open when closed without the elastic engaged.
Note the clever way that Gfeller has exposed the moleskine elastic closure; when not in use, it rests flush against the back cover. When "engaged" around the case, it is tight enough to compress the leather slightly on the top and bottom edges, but not too tightly.
The design of the back cover leaves the envelope enclosure on the moleskine’s back cover accessible.
Read the full review at his blog.