T-3 Miniature Bulbs range in voltage between twelve point eight (12.8) and fourteen (14.0) volts. The letter T in the designation T-3 denotes that the bulb is TUBULAR in shape and that the glass envelope has a Maximum Outer Diameter (M.O.D.) of three eighths (3/8) of an inch or 0.375" inches which is 9.5 millimeters. All bulbs in the T-3 category have a Maximum Overall Length (M.O.L.) of between 1.19" and 1.72" inches. All T-3 miniature bulbs have a C-2V or a C-8 Filament Design.