Looks like Mammillaria sheldonii.

Igor,
It's the same as the one I've been trying to identify for more than a year. I've gotten alot of suggestions, one - mazatlanensis seems to come the closest. Others have thornberi, sheldonii, voburnensis and wrightii. Mine bloomed last summer and then produced a fruit this winter. Here is a link to it.
Dan
Lincoln, NE USDA 5

Here is a link that might be useful: Mamm?

I have this one as an unidentified too! It was labeled as Rainbow Mamm but thatÂs not helpful at all. Mine is budding now, Can't wait for the flowers. It was covered in them last spring. Thanks for the hints on the ID!

Julie

Dan,
Of the ones you've listed as possibles, voburnensis seems to be the most unlikely but the plant linked is so labelled. Quite surprising to me.

Igor,
Mammillarias.net has quite a range of photos you can compare your plant to based on the suggestions given by Dan.

Here is a link that might be useful: Mammillarias.net

Not M. voburnensis. Not M. mazatlanensis. Not M. wrightii. Not M. thornberi. M. sheldonii is a good suggestion, but I would like to offer M. dioica. M. dioica is very variable but some good ID features are the single hooked central spine sometimes with several upper centrals almost like radials, the highly cylindrical shape, and the short strongly green style lobes. The bright red fruit is also helpful for ID, but M. sheldonii fruit is quite similar if a little paler red.

Sheldonii or mazatlanensis seems to be the closest one ... any possibility for this to be a blossfeldiana? I used to have one and bought this cactus because the body reminded me of it ... but blossfeldiana had larger flowers if I remember correctly ...

A few more photos - including of the entire plant - maybe that will help?

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Igor,

I stick to my original suggestion. Still looks like sheldonii to me. I'm not as experienced as shrubs to be able to rule out other species since I know plants can be very variable, but I'm sure I have a plant like this that is labelled sheldonii.

Here is a link that might be useful: My Mammillaria sheldonii

Here is my Mam labelled as sheldonii

Here is a link that might be useful: