Yes, T8 LED bulbs can often replace T12 bulbs because they are the same length and use the same bi-pin (G13) base.

Despite brisk sales of 4-ft T12 fluorescent lamps, the magnetic ballasts commonly used for the lamps’ operation will start becoming part of the past on July 1, 2010, when their continued manufacture ...

T12-to-T8 Conversion Older linear fluorescent fixtures used throughout most of the older buildings on the Western Michigan University campus utilized T12 type magnetic ballasts. This type of ballast ...