Walthers Part # 933-4502, p. 171 Walthers 2021 HO Scale Reference. The Walthers Cornerstone 70' Single-Track Railroad Through Girder Bridge kit is based on one of the most common North American railroad bridge designs. It's part of the Cornerstone Engineered Bridge System and is designed to be compatible with system abutments and bridge piers. Plate-girder bridges are typically used to cross short distances between 30 and 90' 9.1 to 30.4m. Used for many decades, this design is constructed of several steel sections riveted together to form girders. They're known as through types as the track passes between, rather than on top of the spans. It's ideal for use with the Walthers Code 83 Bridge Track 948-886, 948-899 or other trackage of your choice. The kit can be built either as a single-track bridge but includes optional center girder for easy conversion to double-track or wider right-of-way by combining kits. The plastic parts are molded in color and feature authentic rivets and other fine details. As shown the 70' Single-Track Railroad Through Girder Bridge is 9-3/4 x 2-3/8 x 1-5/16" 24.7 x 6 x 3.3cm.