The massive viaduct is suitable for single track HO or double track N-Scale. The smooth back side allows two viaducts to be glued back to back for double track HO or single track O-Scale. Inside arch is same red block pattern as wall. Comes painted and preweathered. Made from urethane foam that cuts easily with most hand tools. Supports 60 lbs. Measures 21" L x 8"H x 2" Deep. Multi-Scale for N-HO-S-O Scales.