Help identifying cactus

[GreenBird]

Hello there, I've got this little plant as a present and I couldn't find what is it.
It had two flower buds (I guess?) that right now are black and covered in what looks like a transparent film.

It's around 3 cm (little bit more than 1 inch) tall and about 5 wide (2 inches). It has spines only on the tips of the tubercles (I'm not sure what they're called).

Thanks in advance.

[img]https://imageshack.us/a/img210/5664/201209212.jpg[/img]

[Wlady]

Trichodiadema densum. Look here https://tiny.pl/hntsl

[GreenBird]

Thank you very much. It's that species indeed. A shame that I won't see its flowers again until next Winter (beginning Spring here).