Small, single filament, 1-3/4" W X 1-1/8" H x 1-5/8" D. !2 volt bulb (48-15021-12V) installed. For 6 volt. order 48-15021-6V separately. 1932-1940 car & pickup
Commonly used as additional brake lights. 12 volt dual filament bulbs installed. For 6 volt or spare 12 volt bulbs see below. 2-1/4" W X 1-1/4" H x 2-3/4" D.