Schedule 40 Black Steel Survey Monument Pipe, 1" x 18" Establish durable survey monuments, property markers and reference points with this 18-inch Schedule 40 black steel pipe . Its heavy-duty steel construction provides a strong, dependable marker for survey control, boundary marking and construction applications. Sold individually. Key Features 1" diameter x 18" long black steel survey monument pipe. Schedule 40 steel construction provides excellent strength and durability. Designed for permanent and semi-permanent survey marking applications. Ideal for survey monuments, property markers, control points and construction layout .