This is the Electro-Harmonix "Enigma" envelope filter for bass. It works perfectly. There are no issues with the switches or control knobs. It has some signs of use, but I have cleaned it simply. Free shipping. This is an envelope filter for bass from Elecro-Harmonix, designed by Mike Beigel, the founder and developer of Mu-Tron. The Riddle is for guitar, and the Enigma is for bass. The functions are the same for both, and they are made with frequency ranges suitable for guitar and bass, respectively. The controls are Blend, 3-mode filter selection (low-pass, high-pass, band-pass), Attack, Decay, Start, Stop, Q, and Sensitivity, allowing for very detailed tone adjustments. Also, you can add Distortion with the left footswitch. You can also control the Frequency with an expression pedal, so you can use it like a wah pedal. It is also possible to output dry and wet signals separately. ■ Specifications - Controls: Blend, Mode (LP/BP/HP), Attack, Decay, Start, Stop, Q, Sensitivity - Distortion equipped - Effect Output - Dry Output - Exp. Pedal Input - True Bypass - Dimensions: 144mm(W) x 119mm(D) x 60mm(H) 550g