Round, incandescent tail lights measure 4 inches in diameter, for use as a stop / tail / turn signal. They come in red durable housing, and are available with or without a reflector lens. A standard three pin plug makes for easy installation.
These standard 6.5 inch oval incandescent lights are for a grommet mount and shown with grommets (sold separately). These are standard three pin connector oval tail lights. The red is a stop/ tail/ turn function, the amber light is for the turn signal.