This kit features precision etched stainless steel parts, real wood deck, tab and slot construction for easy assembly, and detailed illustrated instructions. It includes parts to make a two-track span signal bridge. The basic assembly of this kit has the following dimensions: 5.14" wide overall, 4.65" inside width between towers and 4.3" height overall (to top of handrail). The clearance under the span is 3.0". Expansion spans are sold separately to extend the width of the bridge by 1.82" for each span.