This part of ISO 11922 specifies tolerance grades for the outside diameter, out-of-roundness and wall thickness of inch-based thermoplastics pipes for the conveyance of fluids and manufactured with nominal outside diameters and nominal pressures in accordance with ISO 161-21^[1](see annex A).

It is applicable to smooth thermoplastics pipes of constant circular cross-section along the whole length of the pipe, whatever the method of manufacture, the pipe material or the intended application.