It is mainly a joke/gag product for mathematicians, or a cool office decoration. Nothing you would buy without the background knowledge. But second sentence i

It is mainly a joke/gag product for mathematicians, or a cool office decoration. Nothing you would buy without the background knowledge. But second sentence in the listing: > Like a Möbius strip, this Klein bottle has only one side. In addition, a Klein bottle has no edge - the connection from "inside" to "outside" is smooth, and the bottle has no lip. Is proper descriptive.