Yes, HDPE pipe is available both in iron pipe (IPS) and ductile iron pipe sizes DIPS), sometimes also known as cast-iron pipe sizes (CIPS). IPS sized HDPE pipe has the same outside diameter as black iron or carbon steel pipe. DIPS sized HDPE has the same outside diameter as cast/ductile iron pipe. Typically, ductile iron pipe sizes are available from 4- inch to 36-inch diameters. Iron pipe sizes are available from ¾- inch to 65-inch diameters.