They are advertised as reinforced but. actually it's just cheap plastic. It's hard to tell from the photo, but the inside isn't solid, it's hollow. This means the only support for the entire weight of my trailer is on the sides of the blocks. This flimsy plastic doesn't hold up well. Mine broke after two uses. Because they are hollow, the only contact with the ground is the perimeter of the pad, not the inside. They slipped over me a few times before breaking. I'm just glad I still had theβ¦