A-Shape ("Arbitrary") A21 LED bulbs or general service bulbs, are likely the light bulb shapes we are all most familiar with. The shape is so ubiquitous that A21 light bulbs are likely the first form factor you think of when someone says "light bulb". A21 bulbs are slightly larger than A19 bulbs and typically come in outputs ranging from 75 watts up to 250 Watts in their incandescent forms.
A21 LED Bulb Replacements: A21 LED bulbs recently started to appear on scene a few years ago. The primary target for these are in applications where A21 bulbs are used such as floor lamps, table lamps, sconces and decorative ambient lighting.