This part of ISO 2566 specifies a method of converting room temperature percentage elongations after fracture obtained on various proportional and non-proportional gauge lengths to other gauge lengths. The formula (see clause 4) on which conversions are based is considered to be reliable when applied to carbon, carbon manganese, molybdenum and chromium molybdenum steels within the tensile strength range 300 to 700 N/mm2 and in the hot-rolled, hot-rolled and normalized or annealed conditions, with or without tempering. These conversions are not applicable to a) cold reduced steels; b) quenched and tempered steels; c) austenitic steels. Neither should they be used where the gauge length exceeds mml_m3 or where the width to thickness ratio of the test piece exceeds 20. Care should be exercised in the case of strip under 4 mm thickness, as the index in the formula given in clause 4 in-creases with decreasing thickness; the value to be used shall be the subject of agreement between the customer and the supplier.