Epithelantha micromeris 'Button Cactus' SB1327
Epithelantha micromeris aka the Button Cactus is cold hardy to around -10F if you plant it in a crevice or crack. It has taken -17F for us but is not reliable. These really are a crevice plant and do best when grown harsh. Plants can get baseball sized but are not cold hardy at that size. Plants are also a great container plant and are as spiny as velcro. This seed is from Belen, NM however there is much confusion as to where it actually came from.
Penny sized plants are what is available.