Our vintage quad-loop reproduction bulb is a masterpiece. The glass tip on top of the bulb typical of early 1900s 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 lamp. A19 stands for the shape and size of the bulb (glass). It is the smallest of the 3 sizes. A19, A21, and A23.