A window, shutter or door assembly including a window, shutter or door including a rigid surround frame with a number of peripheral sides and an adjustable mounting frame including at least one frame member relative to each peripheral side of the rigid surround frame of the window, shutter or door and movable relative thereto to abut part of a periphery of an opening into which the window, shutter or door assembly is to be fitted to adjust the size of the adjustable mounting frame in one or more dimensions to fit the opening.