The crested form of this beloved cactus has the typical fans arrangement, which on the whole assume a shape similar to a brain, with a wavy trend never the same from one specimen to another, which therefore makes each plant a unique jewel of its kind. ! Very often we find this cultivar grafted onto other cacti, to facilitate their development and growth that would otherwise be extremely slow. In its normal form Mammillaria duwei is a graceful miniature cactus, with a globular body that does not exceed 6 cm in diameter. The dark green color of the stem is completely covered by flattened white radial thorns that envelop the whole plant, creating an extremely symmetrical effect. In the midst of this perfection single central yellow spines emerge, strongly hooked, which however are not present in all specimens.