From "Mammillaria" by John Pilbeam pag.239-240:
A variant from Lerdo, Durango, is worth seeking out as it is a miniature, prolifically clustering plant, which has a charm of its own.
It was named Mammillaria pottsii var. multicaulis by Reppenhagen, who also named the opposite, large growing variant Mammillaria pottsii var. gigas, from south of the of the species range, al La Cardona in Zacatecas.
Mammillaria pottsii var. multicaulis SB 1062
SB 1062 - Lerdo, Durango, Mexico
Seeds from Mesa Garden - MG 854
From "Ento" Ennio Toso collection - Savona