The Holy Grail is a classic reverb pedal by Electro-Harmonix. Whether you want a spring, plate, or hall reverb, this pedal can do it all and do it well. There is a 3-way dipswitch that allows you to pick which reverb sound you want, and a single knob that acts as a wet/dry mix, letting you dial in just how much of the reverb you want to send to your amp.