The American Petroleum Institute specification API 5L covers seamless and welded steel line pipe. For pipeline transportation systems in the petroleum and natural gas industries.API 5L is suitable for conveying gas, water, and oil.

Specifications for API 5L adhere to the International Organization for Standardization ISO 3183, which standardizes pipeline transportation systems within the materials, equipment and offshore structures for petroleum, petrochemical, and natural gas industries.The technical committee authoring the standards recognized that there are two basic Product Specifications Levels (PSL) of technical requirements and therefore developed PSL 1 and PSL 2.PSL 1 is a standard quality for line pipe where PSL 2 contains additional chemical, mechanical properties, and testing requirements. 

Grades covered by this specification are A25 ,A ,B (and the following "X" Grades), X42, X46, X52, X56, X60, X65, X70, X80.The two digit number following the "X" indicates the Minimum Yield Strength (in 000's psi) of pipe produced to this grade.