Very stable. I was a bit leary onto how these worked, as well. I lifted a mower (60"), and shook it a bit to get the feel of it. It was surprisingly stable. I like the way it sort of "locks" dow onto the pavement. Great investment. There is another one out, that has two legs, but the problem with that, is that it becomes impracticle, because there just isn't enough room to get in there and work.