Systems with T=2 (Listing rings)

• A Band of finite width/height is also Chiral
• A Band with finite width/height and T=2 can have two C₂ axes (D₂ symmetry)
• A journey starting at any arbitrary point on the surface takes one traversal of the cycle to return to the starting point
• For a band with rectangular cross section (width=x, height=y) the journey always starts and ends on the same face (of four)
• In the limit, a cycle with zero width/height lies exclusively in 2D space