HOWARD STREET MASONRY SYSTEM is an integrated system of matching wall, portals & Scale Masonry Components. Multi-Viaduct has deeply textured cut block featuring masonry details on top, sides and inside arched vault. No detail on back side. Polyurethane foam. Measures 13-3/4"L x 4-3/4"W x 1" Thick. (Inside vault measures: 4-1/2"W x 3-1/4" H) FL4158 - "Howard St." Seam Sealers FL4159 - HO Single Stone Block Portal FL4260 - HO Double Stone Blck Portal FL4190 - HO Stone Blck Retaing Wings