PAC AOEM-GM21C System Interface Kit (Add or Replace An Amplifier in Select GM/Chevrolet Vehicles) Adapter used to add or replace an amplifier in select GM/Chevrolet vehicle with monsoon audio system Maintains phasing 20-20000 Hz output Adapter used to add or replace an amplifier in select GM/Chevrolet vehicle with monsoon audio system Maintains phasing 20-20000 Hz output Easy installation