Tong Family

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:

1. E26 T10 9.4″ (aka T30 in metric as this means it is 30mm wide or 1″ wide). These are 9.4″ long
2. 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
3. E26 T10 11.8″. These are really long and great for fancy fixtures
4. 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.