This is a relief valve sensing line hose for the Ames 4000SS & 5000SS assemblies. This hose goes from the valve body to the relief valve and provides line pressure to the back side of the relief valve diaphragm. These hoses often get clogged or plugged. Made of braided stainless steel. Genuine Ames repair part. No special tools are required for servicing but a handy cam check tool is available to assist in removal and replacement of the cam check assemblies.