Very sturdy, thick plastic. A good size that allows for plenty of deck storage items and the plastic will keep things waterproofed, which I needed for storing bags of wood pellets for the rainy winter months. Easy to put together with no tools needed -everything snaps into place in 7 steps. Though for the lid attachment, we found this needed two people ideally since muscle/force is key, as it was only when we popped the middle hinge in first, could we get the side hinges to pop in. Overall, a great deal for the price.