Portfolio Folder. Protect your paintings and drawings in this portfolio made of sturdy 3 mm (1/8 inch) cardboard. Metal protects the corners, three sides tie securely with straps, and the plain white cover is free to be decorated by the artist. Choose from two sizes. Made of cardboard, thickness: 3 mm (0.12 inch), size: 50x70 cm (19.7x27.6 inch), metal protected corners.