18"X24" Heavy #10 gauge transparent vinyl. Heat-sealed edges - no stitching. Vinyl zipper - not cloth. Easy folding allows for smaller working area. Two heat-sealed grommets for hang-up or tie-down. Non-glare surface. Plot on the case with grease pencil. Far more practical than chart tubes - roll up cases without curling your maps/charts. Handles strip charts and topo maps.