eoere 8 Sets 4 Way Structural Pipe Connector, Metal Clamp Fittings, Fit for 1"(O.D. 25.4 mm) Stainless Steel Pipe (Doesn't fit US 1" Electrical-Metallic Tubing) - Amazon.com
Application of Steel Pipe Structure in Buildings - Industry Today - Leader in Manufacturing & Industry News
Structural Steel Pipe
4" X SCH 40 (4.500" OD X .237W) CARBON PIPE STRUCTURAL ASTM A500 GR B