'PENNSY' O-SCALE SYSTEM is a fully integrated system featuring the classic dressed block pattern of the Pennsylvania RR. Each component matches with each other to create a limitless combination of masonry construction. VIRTUALLY EFFORTLESS! Flexible polyurethane foam may be bent to 8" dia radius curve Concave or Convex. Gray primer base finish. Featuring interlocking dovetail edges. Outside dimensions: 14½" W x 7"H x ½" thick. The average size of cut stone measures 5/8" long by 1/4" high. When pieces are interlocked forms a 15" sectional wall. Cover seam butt with FL6158 Seam Sealer.