This knob is for all XDI Arc Audio amps only the new series V2 

Arc audio xdi600.4 

Xdi 450.5

Xdi 850.5

Xdi 850.1 

Xdi 650.1

Xdi 1100.5

Xdi 1100.1

Xdi 1200.6

Ks 600.2

Ks 1200.1

Ks 2500.1

Ks any model that has the phone jack input