these are sizes 18"-30" radius at 2" increments, and also a few straight tracks. The width between the rails is 0.66" I made these for a friend who gave me the dimensions, so I know they're a scale... but not sure which one. (H, N, O, whatever)laser cut these out. They should all be interchangable so you can go right from a 14" radius to a 18" radius turn, or to straight pieces. The flex track fits right on the wall. I did not accoutn for the amount of material that the laser takes away when cutting, so take that into consideration when you're cutting.