This sensing line hose fits the 2 1/2 - 4" Watts 909 Series reduced pressure zone (RPZ) backflow preventers. This sensing line hose supplies the relief valve with line pressure and commonly gets plugged or dry rotted. Your device may have a black rubber hose sensing line. This stainless steel braided hose is a direct replacement. Includes 90 degree fitting that threads into the backflow preventer body. No special tools are required for servicing. Genuine Watts replacement parts.