In the words of MXR:

Take your favorite studio compressor to the stage with the MXR M87 Bass
Compressor. A complete array of controlsAttack, Release, Ratio, Input,
and Outputmakes it easy to fine-tune your sound, from subtle peak
limiting to hard squashed compression effects. Its CHT Constant
Headroom Technology gives you plenty of headroom and clear performance.
This totally transparent compressor allows your full dynamic range to
shine through until your signal reaches the compression threshold, which
is indicated by the ten, highly visible gain-reduction status LEDs.