Flowers large 3-4cm in diameter, purplish pink, in summer, with long narrow spreading stigmata, showy, nearly as large as the plant bodies.
 

Description: Clumping plants with  soft, green or grey-green epidermis. Stems up to 5cm wide, with prominent rounded tubercles usually depressed globose to depressed conical when growing in habitat. While cultivated plant have (frequently) oblong offsetting stems.

Cultivation: This plant is somewhat difficult to cultivate. Needs good drainage as it is rot prone.

Origin: Baja California Sur, Mexico

Conservation status: Listed in CITES appendix 2.

Notes: M. boolii was once placed in the segregate genus Bartschella because of its fruit anatomy and large pink flowers located at the top of the plant. The fruit are red, thin-skinned  and often break off from a basal pore rather than falling whole (like in most Mammillaria).