The approximately 13 rounded ribs create subtle divisions into cusps.

It exhibits 2 to 6 central spines, darker in color and extending up to 5 millimeters, contrasting with the up to 20 marginal spines, thin and approximately 2 millimeters long, positioned on the body's surface.

[3] Accepted subspecies:[4] This cactus species is found in southern Brazil, Paraguay, and Uruguay.

The plant was first described as Echinocactus gracillimus in 1839 by Charles Lemaire, Frailea gracillima derives its specific epithet "gracillima" from the superlative form of the Latin adjective "gracilis," meaning 'slim.

'[5] Nathaniel Lord Britton and Joseph Nelson Rose reclassified the species under the genus Frailea in 1922.