This SAE Recommended Practice applies to those air brake system valves used to control the vehicle service brakes and test procedures defined by SAE J 1859 to measure performance characteristics. This Recommended Practice adheres to standard industry practice of using English units for specifying valve characteristics. 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 SAE J 656 or SAE J 1859 respectively.