If you have added your own goodies to and Allen MOS 1 or 2 type organ and the expression pedal stops working, this is for you. Packaged in pairs they install into the output jacks of the last add-on ahead of the expression pedal. They are bi-directional and one is for the flute channel and the other for the main channel. One pair is required for each computer. Note the photo does not show the actual logo. We had inadvertently shown the 12db attenuator which is not this item but the part looks the same but just has the Harrison Labs Logo.