100% compatibility with OEM lamp 6400 degrees Kelvin 4.75 inch outside diameter T4 lamp tube is 1/2 inch in diameter Formerly sold under Office Depot item #512135 This Caprock brand replacement bulb is a T4 design, which means the tube is 1/2 inch in diameter. The outside diameter is 4.75 inches. The connector for the bulb has four brass pins arranged in a square shape, facing outside the bulb. These lamps come in two sizes (4.75 inches and 5.45 inches), so make sure you are ordering the right lamp, before you buy. The 6400 degree color temperature means the lamp gives bright full spectrum illumination.