I was told by John Dorgan that the clear domes were introduced when Federal went to the larger opening to accommodate the newer styles of 3 & 4 bulb lights. I have seen clear acrylic domes for the older style of rotating 2-bulb lights in the past, however, I don't know if they came about at the same time the 3-bulb beacons with clear domes popularity started. I would think that either the clear or the colored domes would be appropriate for almost any car that had a rotating light on it.