This International Standard establishes the technical specifications for compression springs made from rectangular wires. The parameters set in this International Standard are applicable to springs which are set. This International Standard does not attempt to specify the quality of the springs themselves, nor all of their dimensions (e.g. cross-section), their material or their length of life. The springs are classified into spring rates: light, medium, strong and extra strong. For each spring rate, this International Standard gives a colour code.