The Apollo 61-100 series bronze ball cone check valve with female National Pipe Taper (NPT) threads on both ends is a class 125 valve used for restricting flow to one direction. It has a spring-loaded ball cone that sits against the seat of the valve to block reverse flow. The check valve's body is made of American Society of Testing and Materials (ASTM) B-584 bronze for strength and corrosion resistance. This valve has maximum pressure ratings of 400 pounds per square inch (gauge) (psig) for cold working pressure (CWP)and 125 psig for steam working pressure (SWP), and a cracking pressure of 0.5 pounds psi. It has female NPT threads on both ends for connecting to male threaded pipes with tighter seals than straight threads. This class 125 check valve is for use in water lines, processing plants, and agricultural applications and meets standard Manufacturers Standardization Society (MSS) SP-80 for quality assurance. Class is a standard relating to tolerance, construction, dimension, and wall thickness, but it is not a direct measurement of maximum working pressure. Check valves have two ports and restrict the flow of fluids and other loose materials through a pipe or passageway to one direction. Flow enters through one port and exits through the other, closing when flow reverses or stops. Two common types of check valves are ball cone valves and swing check valves. A ball cone valve utilizes a spring-loaded ball seated against a cone-shaped interior surface to stop the flow of fluid in a forward direction, and a swing check valve has a movable disc on a hinge to block reverse flow. Check valves are rated by their cracking pressure (the minimum upstream pressure required for the valve to operate), and they are used in various water, gas, air, and steam lines. Apollo manufactures ball, mixing, and relief valves, actuators, water gauges, marine fittings, heating and plumbing products, and backflow prevention devices. The company, founded in 1928 and headquartered in Matthews, NC, meets International Organization for Standardization ISO/IEC 17025:2005 and makes products that meet ISO and American National Standards Institute (ANSI) standards.