MK1.5 Switch MKII mode has tons of fuzz with infinite sustain. MK1.5 moode uses one less transistor for less fuzz that cleans up nicely with your guitar's volume.
Built-in Voltage Inverter PNP Germanium transistors require opposite polarity power. Twin Bender has a built-in voltage inverter so that it can share a power supply with other pedals.
External Bias Adjustment  Provides an easy way of fine tuning the NOS (new, old stock) germanium transistors.
Tone Switch 3-way switch with mids-enhanced and fat settings along with stock Tone Bender.
Impedance Knob  Turned fully up is stock Tone Bender. Rolling it back a little will greatly improve tone when used with a buffer, active pickups, wireless devices, wahs, etc. Turn it down more to reduce gain and unlock new fuzz tones.