What is an A-Type Lamp? The (A) stands for Arbitrary, which appropriately fits the rather unique shape compared to the (G) Globe, or (T) Tubular shaped lamps. The shape is virtually unchanged from the very first electric lamps made well over a century ago. The bulbous end of the A-Type incandescent allows for adequate space inside for the filament and supporting structures. Another feature of the oblong globe shape is the increased strength, allowing it to hold a vacuum; an essential element to the incandescent lamp.  At NLI, we stock nearly all voltages, wattages, and sizes including A15, A19, A21, and A23.