Mammillaria formosa is a very variable cactus from Mexico. It is globular shaped and has woolly tubercles that sprout white, bristled spines.
It is generally solitary though it can sometimes produce off-sets at the base.
In spring and summer it will produce a ring of pale pink or white flowers on its top.
Can be grown outdoors in a xeriscape or rock garden but does need to be indoors over winter if temperatures drop too low (under 5c)