What is Welded Steel Pipe

https://www.lordtk.com/galvanized-steel-pipe/

Sizes: Out Diameter: 2-7/8""-6-5/8"", Wall Thickness: as much as 0.813"" Standard: API 5D Application: For properly drilling Petroleum Cracking Tube Sizes: Out Diameter: 1.315""- 20"", Wall Thickness: 0.133""-zero