Our vintage hand wounded quad-loop reproduction bulb is a masterpiece. Featuring a glass tip on top of the bulb typical of early 1900's manufacturing enhances the antique look of this bulb. The quad looped tungsten filament creates a warm welcoming glow that should be enjoyed behind a clear shade or a bare socket. A23 stands for the shape and size of the bulb (glass). It is the bigger of the 3 sizes. A19, A21, and A23. Ideal for any transparent light fixture, both indoor and outdoor.