This purple martin house is constructed with aluminum, which is best suited for the purple martin. It is cooler than plastic. The Starling Resistant Entrance Hole (SREH) is a tried and proven method for helping to eliminate the pesky European Starling. This hole is cut to an exact height restricting starling entry but allowing safe entry for the purple martin. This house has 12 - 6" x 6" rooms. Birds Choice Purple Martin House is fully assembled with rivets. Take the worry out of little screws and nuts with the fully assembled house. Purple Martin Telescoping Pole, PMHD12, sold separately.