Sockets – Small but Important Differences

Even though light bulbs with BA9s, BAY9s, and BAW9s bases look nearly identical at first glance, they differ significantly in the arrangement of their pins:

The BA9s has two pins at the same height that are positioned exactly opposite each other—roughly at the 12 and 6 o’clock positions.

On the BAY9s, the two pins are also at the same height but offset from each other—roughly at the 12 and 8 o’clock positions.

The BAW9s differs further in that the pins are both offset and arranged at different heights.

Therefore, be sure to check the base of your existing light source before ordering.