Young construction workers and architects will spend hours with these lightweight yet durable cardboard building blocks. This 40-piece set features three sizes of "bricks" for constructive imaginative play. Made of premium, extra-thick cardboard for strength, they are easy to assemble and feature a wipe-clean surface. The red blocks hold up to 150 lbs! This product is certified by the Forest Stewardship Council. FSC certification ensures that products come from responsibly managed forests that provide environmental, social, and economic benefits, and that forests are protected for future generations. Please note that FSC certification applies to new inventory only (FSC C156584)