The E flat diminished chord is a 3-note chord consisting of the notes Eb, Gb and Bbb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Ebdim.
Chords that are a superset of Ebdim. The chords include more notes but always Eb, Gb and Bbb.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the Ebdim chord. Feel free to save or share the image as needed.