JIS G3444 specified welded or seamless carbon steel tubes for general structural purposes, civil engineering, architecture, steel towers, scaffoldings, struts, piles for suppression of landslides and other structures.Grade:STK290,STK400,STK490,STK500,STK540Outer diameter: 33.4-660mmWall thickness:2.1-22mmLength:0.8-18mManufacture Method: Hot Rolled.Surface Treatment: Coating, Painting, Galvanized, etc.