piano chord
B♭sus4
B♭1E♭4F5
The third replaced by the fourth, which leans on the third it is standing in for.
Written the other way round it is A♯sus4 — the same twelve keys on a piano, a different piece of notation.
What is true of it
B♭sus4 is B♭, E♭ and F — 1, 4 and 5 counted from B♭.
These are also the notes of E♭sus2/B♭ and D♯sus2/B♭. Which name is right depends on what is underneath and what came before — the notes alone do not decide.