Here is a capacitor looking outdoor light cover. There are many variations of this to accommodate the different types of light bulbs Older versions may have thicker glass but as far as I know the ends always have a rubber gasket on the threaded side and the opposite side is always sealed to keep water away from the bulb. I have seen them in larger sizes in colored glass used for the border of runway at airports. Red glass ones sometimes are used on top of electric poles near helicopter landing areas such as next to a fire station or hospital.