Found in Guanajuato state in central Mexico, Mammillaria crinita f. zeilmanniana is a clumping cylindrical cactus to 5 inches tall and 3 inches across. It produces flushes of white or magenta flowers throughout most of the season.
     This came from Tohono Chul allready in flower. Since it's a clumper and produces nice flowers I think it will go in the garden this year.

A closer view

Closer still