From the Aguilar website:
The Filter Twin® uses two identical filters sweeping in opposite directions - one up in frequency, one down in frequency - to give classic 70's-inspired funk sounds or completely new and original filter tones. Two filters sweeping at the same time give you a more organic, vocal quality and allow you to get expressive new sounds that you can't get from other pedals.
The Filter Twin® offers unique filter effects via an intuitive four-knob layout. The blend control allows you to adjust the mix between the filters. The threshold control determines how sensitive the unit is to different playing styles. The velocity controls determine the speed of each filter.
Pedal is in mint condition. $125 shipped in CONUS.