This RG-2 relay valve is a replacement for the Mack air brake system, sold as a single unit. Mounted in the brake circuit, it applies and releases air to the brake chambers on command, positioned closer to the chambers than the treadle valve to cut down on lag. It fits applications originally equipped with the Mack valve it replaces.Interchanges:Mack 5396-KN28500LRV-3637FeaturesRG-2 relay valve designSold as a single unit (sell pack: 1 EACH)Categorized under Air Brake PartsTech SpecsType: RG-2 Relay ValveSell Pack: 1 EACH