I've never owned these, but I've seen a lot of them. A short columnar mammillaria, with upright and somewhat thin stems, clumping, plain spination and magenta flower (though a white blooming variety exists). It is considered to be one of the easy-care mammillarias. It can be mistaken for matudae (which has much more compact spines) and spinosissima rubrispina (which has denser spination and small gaps in between its tubercles).