Pessina Tubi also provides seamless and welded steel pipes according to the standards Pipes Api 5L / ASTM A 106 GR.B - ASTM A 333 GR.6 . API (American Petroleum Institute) is the leading US organisation in the field of petrochemical and chemical engineering. The API 5L norm, in particular, defines the characteristics of pipes intended for the transport of water, gas and oil.