The pet stair is very good quality and of equally good value.  The only reason I gave it 4 out of 5 stars is because the depth of the step treads is too shallow in my opinion.  I have a 12 lb. dog that will not use the stairs because her paws slipped off on the way up the first time she used it.  Previously, we owned a 3 step unit (not the same manufacturer) that had deeper treads that our dog used all the time without incident.  Unfortunately I could not find the same unit and took a chance on this pet stair.  Again, not that it will be an issue for other users, but for us it isn't working because of the depth of the step treads.