It provides a connection for one set of RCA cables to provide an audio signal to an external amplifier, and also an additional circuit with remote wire for the remote amplifier turn on wire. Fitment: for Chevy for GMC for Cadillac OE Number: 70-2105 Note: Only compatible for factory non-amplified systems (base radio), but not the factory amplified stereo systems. Package Included: 1 x Subwoofer Amplifier Plug and Play Wire Harness