Valterra Optilite Replacement 18" Fluorescent Bulbs are rated at 4100 Kelvin for a long-lasting, natural white light output. Designed with a bi-pin T-8 base for use with a ballast in a standard fluorescent fixture.• Bi-pin T-8 base construction• 4100 Kelvin for a natural white light output• Up to 2500 hours of use• Must be used with a ballast in a standard fluorescent fixture• 12V / Operates at 15 watts per bulb• Bulbs are not dimmable• 2-pack Bi-pin T-8 base construction For use with a ballast in a standard fluorescent fixture Operates at 15 watts per bulb | Valterra Optilite Replacement 18" Fluorescent Bulbs, 2-Pack in White