OK, we had another strange bulb go out. It has a medium E26 base and is about 5 inches long, so how to get a replacement? This led me back to the whole shape vs. base labyrinth that is light bulb sizes, so as a refresher, E26 means an Edison base (which is also called a medium base and is 26mm in diameter). Then there is a curious collection of T designations which curiously refers to the diameter of the bulb.
There is then a convention for how long the bulb is given that it has a certain diameter so you have to look on the package to make sure the length is correct
The other confusing thing is the same T designation is used for fluorescent tubes, so you can have a fluorescent T8 which is completely different from the E26 version with T8, so make sure you know what base you are getting.
I couldn’t find any map of the T designation to diameter, but here are some observations based on what I’ve bought in the past:
- E26 T10 9.4″ (aka T30 in metric as this means it is 30mm wide or 1″ wide). These are 9.4″ long
- E26 T10 7.3″. These are 7.4″ long, so be careful. This like the one above is a decorative LED, so it has a visible filament
- E26 T10 11.8″. These are really long and great for fancy fixtures
- E26 T10 5.1″. These are frosted and are LEDs
The final criteria is the color of the bulb. Indoors, we like the warm 2700-3000K soft white, but outside if you want to guard something, the much more blue 4-6000K might suit.
