Rings produced by cutting a strip that has been given 
half twists and been re-attached into 
equal strips (Ball and Coxeter 1987, pp. 127-128).
Paradromic Rings
See also
Möbius StripExplore with Wolfram|Alpha
References
Ball, W. W. R. and Coxeter, H. S. M. Mathematical Recreations and Essays, 13th ed. New York: Dover, pp. 127-128, 1987.Referenced on Wolfram|Alpha
Paradromic RingsCite this as:
Weisstein, Eric W. "Paradromic Rings." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ParadromicRings.html