Marketing InformationARMSTRONG flex flange is a rotating flange designed to allow maximum installation flexibility regardless of pump flange orientation. Flex flange units are available with a spring check valve to prevent the heating medium flowing in the wrong direction in the event of gravity circulation. The flex flange integrates a two-bolt flange connection with a full port ball valve. This practical all-in-one design reduces the number of plumbing connections and results in a more reliable and easily serviced hydronic system.