Mammillaria Voburensis subsp. eichlamii
These are relatively small cacti, some with relatively small spines. Some Cactus are mature at just an 1 inch or so tall, though some larger barrel species can grow over 1 foot in diameter and nearly 2 feet tall. Some sucker and some seem to be solitary.
It appreciates strong light, but many species dislike more than four hours of direct summer sunlight. Allow the soil mix to become nearly dry between waterings, but then water thoroughly. Suspend watering in the winter, but mist occasionally.
During the growing season, fertilize with a cacti fertilizer mix.
It is used as an ornamental, It is an excellent plant for container growing. It always looks good and stays small.