This is a favorite cactus for me. I have always had easy luck with it. My personal specimen is about 12” tall and 8” in diameter.
Your N. magnificus will ship bare-root but will be similar to the small one pictures.
Botanical Name - Notocactus magnificus, Parodia magnificus
Common Name - Balloon Cactus, Ball Cactus
Sun - Full sun, some shade
Cold Hardiness - 25-32F — I don’t let mine get below 40F.
Native to South America.
Large photo of N. magnificus with yellow flower :
Claire H. from New York City, USA, CC BY-SA 2.0 via Wikimedia Commons