This Marcgravia came into cultivation around 2012, but has not been widely available due to its slow growth habit.  It is not difficult to grow, just slow.  Like most Marcgravia it is capable of getting larger outside the terrarium.  Its leaves stay around an inch, and are edged with white that only becomes more prominent with age.  It is from Colombia.  The second pictures shows it next to a white seam species from Ecuador, which is much smaller!

Available plants are well-rooted in 2″ pots. They will be shipped potted. The last photo is representative of the size plant you will receive.