Armstrong 110223-306 1/25 Horsepower Astro 230SS Wet Rotor Circulator, Stainless Steel Extra quiet operation for residential, office commercial, hospital or educational institutions Designed for use in open-loop heating applications, including hydronic, radiant heat e-Coating on the inside of the pump provides an enhanced corrosion protection for longer pump life and less debris in the system Large wiring box and convenient plug-in terminal strip Standard flange (2-1/2" OC holes), compatible with other brand flanges & isolation valves