Medium Base One-Piece White Urea Outlet Box Mount Incandescent Lampholder, Keyless, Single Circuit, Top Wired, - White Leviton produces lamp holders for virtually every light source equipped with incandescent, fluorescent, or CFL lamps. Lamp-holders include incandescent medium base, and specialty sizes & fluorescent lamp holders, in addition to a large line of porcelain lamp holders including pulse-rated mogul-base products, and an extensive selection of devices for high-intensity lamps.