Yes, it has a waist because when I got it it had not been watered for months. Some people get cactus plants in little ceramic dishes and they figure that they are cactus, so the don't need water. The person who had this one had 2 Mamms, this
Rebutia and a Gymno. in a dish garden. She knew that one should be careful how much water they get, so she gave it a tablespoon (about like your soup spoons) of water per month. The Gymno. died, and so did one of the Mamms. I have a normal one of these too, maybe I can find the photo and post it as a blooming plant in a week or so.