What is Welded Steel Pipe

https://www.lordtk.com/pe-coating-pipe/

Sizes: Out Diameter: 2-7/eight""-6-five/8"", Wall Thickness: as much as zero.813"" Standard: API 5D Application: For nicely drilling Petroleum Cracking Tube Sizes: Out Diameter: 1.315""- 20"", Wall Thickness: 0.133""-zero