The City Classics HO Scale Rooftop Details set provides a wide range of items typically found on roofs of small to medium sized buildings. The set includes two rooftop stairways with a choice of different style doors and vertical or horizontal siding, two skylights, four chimneys, eight access hatches and 20 vent pipes in assorted styles. One Rooftop Details set includes enough parts to finish the roofs of multiple structures. These are injection molded styrene parts. See the entire line of City Classics 195 HO Scale building detail parts.