Woodland Scenics C1263 Culvert Masonry Arch (Pack of 2) HO Gauge Use Earth Colors™ Liquid Pigment to detail Culverts in your choice of colors. Approximate outside dimensions: 2 5/16" w x 2" d x 1 13/16" h (5.87 cm x 5.08 cm x 4.6 cm). About Terrain Structures Tunnel Portals, Retaining Walls, Culverts, and Roads reinforce natural terrain contours and add functionality, realism and interest to your layout.