Gymnocalycium gibbosum

Gymnocalycium gibbosum  is a quite variable species. This polymorphism has led some authors to describe a lot of unnecessary varieties.
Stem: Deep glaucous-green, olive green, brown to grey-black, discoidal that became elonged with time 10-25 cm tall, up to 12 cm in diameter, the apex is slightly woolly.
Ribs: 10-16 straight, divided in well distinct angular ribs.
Areoles: Whitish-grey, elonged.
Radial spines: 5-7 (-9) 20-25 mm long slightly bent against the plants body, clear brown with a darker base when young, becoming whitish-grey with a black base as they age.
Central spines: 0-2 very similar to the radials.
Flowers: Infundibuliform in the nearest periphery just around the apex 45-60 mm long, 60-65 in diameter. Tepals ivory white with a brownish mid rib or occasionally reddish, throat greenish with a basal reddish area. Style white-greenish, stigma white. Anthers cream coloured.
Fruits: Globate or fusiform, 20-40 mm long green with white bordered scales.
Remarks: Seems to be a pretty variable plant you might get some other names which are effectively the same plant.... and also not sure all plants identified as this are really this.

Pot size 4.0", you will receive a (sami bare rooted, with some soil) similar plant shown in pictures.

"Sizes are approximate" every plant is slightly different then others, due to your screen setting and different screen type.