CFValve Constant-Flow Valves attach to your existing Chapin， Solo， Hudson or Jacto sprayer nozzle to help maintain a consistent flow rate with ±1.5% accuracy， regardless of pressure variations. Constant-flow valves reduce drift， and the valve automatically closes if the output pressure drops below the preset valve pressure. 14.5- and 21-psi valves help control drift when applying herbicides and are for handheld and backpack sprayer use. 29-psi valve is designed for 12V and motorized sprayers. Includes two adapters: 11/16" to 3/8" and 3/8" to 11/16".