Pipe Calipers are unique outside diameter calipers created and manufactured by Oregon Rule Co. The Pipe Caliper is a tool often useful to Engineers, Draftsmen, Pipe-fitters, Contractors, Carpenters, Plumbers, and related industries. This is a fractional measuring unit, which reads in inches. This Pipe Caliper can measure pipe sizes up to 16" in diameter. A conversion chart printed on the caliper translates measurements of the outside diameter to the nominal interior diameter dimension. Also, there is a conversion chart that reads from fractional to decimal. The swing arm can extend into a 14" long ruler. These calipers are made from a durable lightweight black anodized aluminum.