It should be Mobius ring. Various translations are different.

"Mobius ring" is a real concept, which comes from an ancient science-mathematics. 1858, the German mathematician Mobius (1790- 1868) and another mathematician independently discovered the unilateral surface. He used to be the teaching assistant of the famous mathematician Gauss. This surface can be obtained through an interesting experiment: take a rectangular paper tape and observe it carefully, and you will find that it has two sides and four sides. After twisting one short side by 180 degrees, it is bonded with the other short side to form an 8-shaped ring. At this time, if you look at it again, you will find that this paper tape now has only one side and one edge. This is the famous topological structure, and the Mobius belt (also translated as Mobius ring) named after the German mathematician himself became famous. The birth of Mobius ring makes topology, a branch of mathematics, flourish.