Five pieces of track make up one-quarter (90 degrees) of a 71" diameter circle (a full circle is 360 degrees). In general, 35.5" Radius Curved Track is best used to make wide, sweeping railroad curves to accomodate longer locomotives and rolling stock, and permit mainline operation at higher speeds. It can be placed on the outside of 33.25" radius curved track for excellent double-track mainline realism, and it can also be used to quickly lay track on a behind-the-scenes helix.