T8 lamps require an electronic ballast specifically designed to operate lamps at a lower current than T12 lamps. Whenever T12 lamps are replaced with T8 lamps, the ballast must also be replaced. Install an electronic ballast for optimum light quality and efficiency; electronic ballasts don?t flicker or hum, and they use less power! T12, T10, and T8 lamps can all use the medium bi-pin base, which allows T8, and T10 lamps to fit into the same luminaires as T12 lamps of the same length. T5 lamps have a different base, and are shorter than T8s, so new lumenaires are needed.