What are A21 bulbs?
A-Shape ("Arbitrary") or general service bulbs are likely the light bulb we are all most familiar with. It's shape is so ubiquitous that this is 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.
Incandescent A-Shape Ban
Back in January 2012, 100 Watt Incandescent A-Shape bulbs were no longer available for sale in retail stores. This phase-out continued until 40 watt bulbs were eventually phased out in January 2014.
A21 LED Replacements
There has been significant progress made over the past few years on developing and perfecting the A21 LED. With over 6 billion bulbs in service worldwide, the opportunity is enormous. A21 LEDs are now commonly used for higher wattage replacements and are found in wattages typically ranging from 75 to 100 watt equals. The larger A21 size allows for more heat sink surface area and as such is a popular choice for manufacturers looking to build such higher wattage replacements.
Buyers purchasing A21 LED bulbs should be aware of the larger size of such bulbs and double check dimensions to ensure a proper fit.