Fender virtually wrote the book on reverb and tremolo with their various historic amplifiers from the early 1950s through the late 1960s, and they have packed their most revered, most iconic versions of BOTH into this one, tremendously vibey pedal. Both the tremolo and reverb sides of this pedal boast three different, distinct models. The tremolo side features Optical (mid sixties tremolo as found in the '65 Deluxe, Twin, etc), Bias (pulsy goodness ala Fender Princeton, Vibroverb, Tweed Tremolux, Tweed Vibrolux) and HM, which is Harmonic tremolo which delivers lush phase-shifting style tremolo as found on Fender's short lived, but highly desired early 60s Brown amps (Fender Concert, etc). The reverb hosts '63 Reverb (a la Fender's original standalone, tube driven reverb units), '65 Reverb (as found in iconic black panel Fender amps), and something a little different in the form of a Studio Plate emulating reverb with rich, dimensional modulations. Part number 0234541000 .