Quize for Hywel

It's difficult to identify a cactus. There are so many species, and so many varieties of each species ... and the same variety can look very different in different locations.

This one is definitely a Mammillaria.
Could be M compressa
M decipiens
M polythele
???

Does it flower ? Maybe it would be easier to identify with flowers.

I have never seen it bloom....but I am happy with the name of the group ...... Mammillaria , thank you.
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I am pretty sure it is M. compressa . I googled the names you provided me with and the M comressa looks like the one in the pot. Thank you Hywel. Now I can put all my pictures under that name.

That's good :o)