Two filters in one, though they can be chained. This is a passive device, no power used (think - same thing as the tone knob on your electric guitar).
Relatively easy build, through there were two nits about the boards fitting together and the knobs, but overall fine.
Sound-wise, it’s OK. Passive, so not a whole lot of activity, but does produce some mellow filtering. Not going to be in my main rack.