This may sound simple to some but I bought a couple exterior light fixtures. They say only use type A-19 light bulbs or lamps. From what I guessed looking through the net I think this means no CFL energy saving bulbs. What exactly is an A-19 type light bulb? The light fixtures I bought have a sensor and dual-brite dimmable lighting capability which I don't even plan on using. I want it on at 100% brightness at all times.
It defines the physical size of bulb that can be accomodated.
The most commonly used A-series light bulb type is the A19 bulb, which is 2 3⁄8 inches (60 mm) wide at its widest point, approximately 4 3⁄8 inches (110 mm) in length, and has a one-inch wide (type E26, i.e. approximately 26 millimetres wide) Edison screw base.
Any CFL that fits in the space provided should work
Some LED lamps sometimes need airflow to keep their temperature in operating ranges. So might have issues in a fully enclosed fixture