This Outdoor Water Solutions backyard windmill conversion kit converts an ornamental backyard windmill into a fully functional windmill for ornamental and/or koi ponds. U.S.A. Application: Converts an ornamental backyard windmill into a fully functional windmill for ornamental and/or koi ponds, Includes: Diaphragm compressor, air line, and airstone Aerates ponds up to 300 square feet at 2 1/2–3ft. depth