This feeder has metal tops, bases and ports that are made from zinc die-castings to last a lifetime. The tubes are clear polycarbonate that is UV-stabilized to withstand the sunGÇÖs rays. The feeding ports are designed with optimum perch-opening dimensions for birds to feed comfortably. The ports also have a "Rain Guard" lip to help prevent rain from running down the side of the tube and into the feed supply. Also, drain holes help keep the food supply dry. An angled base insures that birds can always get at even the last few seeds - this avoids seed waste or buildup in the bottom.