Pivoting T-Post Clamp, Fits 16 mm Holes – Strong Hand Tools
Set 2.1 for System 16 - 16mm Bored Hole Accessories (4-163200.1) – Siegmund Welding Tables USA (An Official Division of Quantum Machinery)
Inserta Clamps, Fit 16 mm Holes – Strong Hand Tools
Inserta Clamps [16 mm] – Workbench Pros
16mm 22mm 28mm DIN Series Inserta Welding Table Clamps with T Handle - China Adjustable Welding Clamp, Welding Table Clamp | Made-in-China.com
Lincoln Electric Welding Clamp Set - 8 Clamps for 16mm Fixture Holes, Secure Round and Square Tubing, Black in the Welding & Cutting Accessories department at Lowes.com