3/8 ply, I believe (dragged it out of the scrap bin). The frame is 10x12, I believe, and made from the scrap pieces that come between layers of wood at Lowes, they toss 'em in a dumpster and let me rummage. I like the knotty, beat-up, rustic look of that wood, but its pretty green (literally, its greenish in color) so each piece goes through several sanding cycles from 80grit up to 320grit to get it smoothed up a bit and take the surface layer of crud off. Still ends up with a light greenish tint, but it takes a stain really well, and for the price, I can't complain.