Check the listing for details. Watts B911s-M3 Comb Fill Valve/Backflow Preventor, 1/2In. Width: 2.940, Condition: New, Made in US. Listed at 190.00 USD. The Watts B911s-M3 Comb Fill Valve/Backflow Preventor is a 1/2 inch water valve designed for preventing backflow in plumbing systems. With a California Prop 65 Warning, this valve is manufactured by Watts in the US and features a boiler feed valve function. It has a weight of 3.1500 pounds and dimensions of 5.250 inches in length, 2.940 inches in depth, and 2.940 inches in width. This product is suitable for water media and does not include a battery or come in a custom bundle.