Abstract: A plurality of elongated shutter slats of extruded rigid plastics material have co-extruded cores of rigid plastics foam material, and injection molded plastic end caps are attached to opposite ends of each slat. The end caps have elongated flat base portions and retention lugs with head portions integrally connected to the base portion by reduced neck portions. The lugs of the end caps are retained within undercut channels in extruded metal side rails. In one embodiment, each end cap is secured to a slat by screws extending through two retention lugs and into the foam core. In another embodiment, the end caps are secured to hollow slats by integrally molded bosses which project into cavities within hollow slats and are cemented to the walls of the slat.