Easy cleaning and maintenance with one-piece jar top bonnet Rain Bird exclusive fail-safe design Heavy-duty, professional design for a life-time of trouble-free operation Flow control models regulate the flow of water sprinklers to avoid misting Vacuum breaker prevents backflow contamination to keep drinking water safe External bleed to manually flush system of dirt and debris during installation and system start up Operates automatically with any standard 24 volt sprinkler timer Meets I.A.P.M.O listing specifications.