The "flats" are actually 18" square tiles made from chemical-free, recyclable paper pulp that's been molded into one of several textured mod-looking surface patterns. They're modular, fairly simple to apply, and removable (although not re-useable), so they're a great cosmetic fix for plain, ugly or damaged walls.
The tiles can be left raw but they're designed to be painted, so you can use them to bring color to your walls as well as texture. Wall flats come ten to a box. A box costs $84 and will cover 22.5 square feet of wall.
(Edited from a post originally published 11.13.06 - CB)