Be sure to read the dimensions on these pet stairs because they wound up being bigger than expected. It's fine and actually worked out pretty great, since we have a platform bed with storage beneath it, but I was shocked to see how big they were! That being said, I love that these fold and that each step is kind of carpeted so paws don't slip. Once unfolded, the stairs are decently sturdy, but I'm not sure that they would work for a large/heavy dog. 

Four stars because I wish there was maybe an extra arm piece or something on the bottom that could be locked in place to really keep them from folding. That's my only worry with this design. Still a great buy for pet owners and they work really good for helping older pets get on the bed or furniture.