Option Knob OKnob Guitar Effects Accessory Classic OKnob Guitar Effects Accessory Classic The OKnob uses a friction-based grip to replace your factory knob and fit tightly in its place It is made out of very durable materials so that it can withstand being tossed around in your gig bag Traditional effects pedal knobs may be different sizes on the outside, but they all have a very similar size hole on the bottom side of the knob Option Knob designed 2 different OKnobs, the Classic and the Boutique, which cover the entire range of knob shafts so that it will ensure a snug fit when you replace your factory knob