5 fluorescent bulbs are 5/8" diameter fluorescent tubes rather than the standard 1-1/2" diameter. This slim profile makes the T5 Fluorescent system more efficient than fixtures that use standard fluorescent tubes. T5 fluorescent bulbs also put out more light than standard fluorescent lamps, power compacts and VHOs. Important Shipping Information: Minimum order of 2 (two) T5 lamps, (Mix & Match), to qualify for our standard shipping fees.