Bb Quartal (So What), 3rd inversion (B# in the bass)
Also written as Bb quartal/B#.
Notes, from the bass up
B# (bass)E#A#D#G#
The same notes as Bb Quartal (So What) (B#, E#, A#, D# and G#), rearranged so B# is the lowest note. Use it to move between chords with smaller jumps across the keyboard.