The commom materials ---20# and Q345 Technical standard:API 5LGR.B , ASTM A106/A53 GR.B; High-pressure boiler pipe,fluid pipe seamless steel pipe1. Size: 1/4'' to 24''2 Standards: ASTM, API, DIN ,JIS 3 Surface: Oiled,varnished or black painted to prevent rust 4. Steel Grade: 10#, 20#, Q345 etc API 5L seamless steel pipe