The door jamb is constructed of a paintable hard polymer shell with an interior close cellular structure that prevents water absorption while offering 2 times the screw holding strength than wood. Three 4in. steel ball-bearing hinges were applied. Prefinished at our factory allows us to finish all edges of the panels, rails, and styles prior to assembly of the doors. This is extremely important for the long life of the doors, minimizing panel issues. The finish is a 9-step oil-based polyurethane process.