ASTM A270 standard is about Seamless and Welded Austenitic and Ferritic/Austenitic Stainless Steel Sanitary Pipes/Tube.

ASTM A270 standard covers grades of seamless, welded, and heavily cold worked welded austenitic and ferritic/austenitic stainless steel sanitary pipes/tubes intended for use in the dairy and food industry and having special surface finishes. Pharmaceutical quality may be requested, as a supplementary requirement.

According to ASTM A270, arithmetic average surface roughness normally reported in microinches or microns; a measurement of surface roughness usually performed by moving a stylus in a straight line along the surface, although other methods may be used.

In ASTM A270 Standard, for stainless steel pipes/tubes with a specified wall thickness of 0.049 in. (1.24 mm) and greater, variations in outside diameter from those specified shall not exceed the amount prescribed in ASTM A270 Table 2. For stainless steel pipes/tubes with a specified wall thickness less than 0.049 in. (1.24 mm), the diameter tolerances shall be a matter for agreement by the manufacturer and the purchaser. When stainless steel pipes/tubes  >4 in. (101.6 mm) outside diameter is ordered, additional ovality may be required for thin wall stainless steel pipes/tubes . Thin wall stainless steel pipes/tubes applies when the specified wall is less than 0.150 in. (3.81 mm). When thin wall tubing is ordered, the maximum and minimum outside diameter at any cross section shall deviate from the specified outside diameter by no more than twice the permissible variation in outside diameter given in ASTM A270 Table 2; however, the mean diameter at that cross section must still be within the given permissible variation.