This standard gives the requirements for sleeving having the property of expanding its internal diameter when compressed longitudinally and thereafter returning to its initial diameter after release of the compressing force. It is constructed of polyethylene terephthalate monofilament yarns suitably processed to provide the mechanical ability to conform in the manner described above. These sleevings have been found suitable for use at temperatures up to 130 °C. This sleeving is normally supplied in internal diameters between 6 mm and 63 mm and in three levels of wall thickness (thin, medium, and thick). It is normally supplied in the following colours: black, white, brown, red, orange, yellow, green, blue, grey, and natural. Because of its open construction, this sleeving is normally used to provide air-space insulation. Therefore, no requirement for breakdown voltage is specified in this standard. (Any value for this property should be given in the purchase contract, but a typical value is 1,5 kV/mm wall thickness, although a linear relationship cannot be assumed.) However, it serves to provide mechanical protection to circuit components such as wires, sleeves, and flat cable over which it is applied as a containing wrap or harness. Materials which conform to this specification meet established levels of performance. However, the selection of a material by a user for a specific application should be based on the actual requirements necessary for adequate performance in that application and not based on this specification alone.