This part of ISO 1874 establishes a system of designation for polyamide (PA) thermoplastic materials, which may be used as the basis for specifications. It covers polyamide homopolymers for moulding and extrusion based on PA 6, PA 66, PA 69, PA 610, PA 612, PA 11, PA 12, PA MXD6, PA 46, PA 1212, PA 4T, PA 6T and PA 9T and copolyamides of various compositions for moulding and extrusion. The types of polyamide plastic are differentiated from each other by a classification system based on appropriate levels of the designatory properties a) viscosity number, b) tensile modulus of elasticity and c) presence of nucleating agent, and on information about chemical structure, intended application, method of processing, important properties, additives, colour, fillers and reinforcing materials. The designation system is applicable to all polyamide homopolymers and copolymers. It applies to materials ready for normal use, unmodified and modified by colorants, additives, fillers, reinforcing materials, polymer modifiers, etc. This part of ISO 1874 does not apply to monomer casting-type polyamides of PA 6 and PA 12. It is not intended to imply that materials having the same designation give necessarily the same performance. This part of ISO 1874 does not provide engineering data, performance data or data on processing conditions which may be required to specify a material for a particular application and/or method of processing. If such additional properties are required, they shall be determined in accordance with the test methods specified in ISO 1874-2, if suitable. In order to specify a thermoplastic material for a particular application or reproducible processing, additional requirements may be given in data block 5 (see 3.1 and 3.6).