AMH2K-RX AQUA SHIELDTM Circulator for Outdoor installation. on TANKLESS HEATER WITHOUT BUILT-IN PUMP ON DEDICATED RETURN LINES, For up to 600 Ft. of total pipe length and tankless minimum GPM .5 or more: AMR-SFV1AXLT1stainless high speed circulator with 4 bolt flange connection body, 10 ft. line cord, with outdoor enclosure, automatic built-in timer, built-in sensor/switch (115°-125°), water, sprinkler, bug, freeze protected, anti-tampering locking device tab. FK75S Stainless 3/4″ Flanges included. Patent pending.