The Milwaukee Valve 2974-M series iron swing check valve with flanged connections on both ends is a class 125 valve used for restricting fluid flow to one direction. It has a hinged disc that swings onto the seat of the valve to block reverse flow. The valve body is made of American Society of Testing and Materials (ASTM) A-126 cast iron for strength. This valve has maximum pressure ratings of 200 pounds per square inch (gauge) (psig) for water, oil, and gas (WOG) and 125 psig for steam working pressure (SWP), and a cracking pressure of 0.5 psi. It has flanged end connections for semi-permanent yet reversible connections to tubing. This class 125 check valve is for use in water lines, processing plants, and agricultural applications and meets standard MSS SP-71 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.

The Milwaukee Valve Company manufactures manual and actuated valves, controls, and control accessories. The company, founded in 1901, and headquartered in New Berlin, WI, meets International Organization for Standardization (ISO) 9001:2008 and 14001:2004 standards.