German 3 piece moisture-proof endcaps. - Will fit 1.5" T-12 VHO, HO, NO bulbs. - Rubber o-ring to help protect socket from humidity and moisture from your aquarium. - Sold in Pairs. - Mounting screws are included. The 3 piece design allows easy bulb replacement, as once the base is screwed into place, you only have to unscrew the middle ring to remove the bulb.