I have used this extension for months. It is simple, easy to use, and support desktop notification of fluxbox for both RHEL7 and Fedora 25.

However, recent update broke the stats, thus no statistics.

I like the simplicity of this add-on. It just consists of 5 buttons - a button for 25-minute Pomodoro chunks, 3 buttons for 5-, 10-, and 15-minute breaks, and a button for resetting the timer. While the timer is running, it also displays the remaining minutes on a small number on the toolbar icon, which is pretty convenient.

Unfortunately, it's so simple that some basics are missing.
- No alarm sound when timer is finished
- Break timer doesn't automatically start
- Doesn't really support the long break after 4 Pomodoros

Would use it again if the above features are added.