The E flat diminished seventh chord is a 4-note chord consisting of the notes Eb, Gb, Bbb and Dbb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Ebdim7.
Interactive piano diagram for the E flat diminished seventh chord
Chords that are a subset of Ebdim7. These contain less notes but all of them are included in Ebdim7.