From the publishers website:
GameMastery Flip-Mats are designed to make your game portable and affordable. They're made with durable, laminated card stock and can handle dry erase, wet erase, and even permanent marker!
Flip-Mats are constructed of durable laminated card stock (~70 lb paper—comparable to that of a restaurant menu). They measure 24" by 30", and quickly and conveniently fold down to 8" by 10" (slightly smaller than a sheet of notebook paper).
GameMastery Flip-Mat: Basic features a 1"-square grid on both sides. One side features a stoney-grey patterned background, and the flip side features a sandy-brown texture. The 1” grid extends fully to the edge of the maps for a full 720 square inches of usable area.