This SAE Recommended Practice applies to those air brake system valves used to control the vehicle service brakes and test procedures defined by SAE J1859 to measure performance characteristics. Purpose The purpose of this document is to provide a means of identifying vehicle air brake system components with performance (input-output) characteristics. This labeling procedure intends to identify and facilitate proper in-service valve replacement. Nomenclature and test procedure are defined in either J656 or J1859 respectively.