DOD 240 Resistance Mixer

I have two, the lighter version pictured in older and comes with the box.

This is a 4 to 1 or 1 to 4 audio routing tool. This could be used from one guitar into 4 amps, or from 4 instruments into one input/pedal chain.

Excellent for 2 guitars, mandolin, and violin into a single DI for example.

Also having 4 different electric guitars with levels adjust to behave similarly into your pedal chain.

Two of these could be used to run a parallel drive chain where you have a tube screamer and a big muff running parallel to keep clarity and distortion and then mix the signal back down to a single channel to go through delay and reverb.