Amplified external 8 OHM 4in speaker with 6 foot cord & 3.5 MM plug & 12V power cord. With power / bypass switch. Amplified speakers are designed to give additional attenuation in environments when the radio alone isn't able to get the audio level high enough.
Amplified External Speaker
Connect the red wire to a 12V DC positive source for the amplification, plug the speaker jack into the radio/scanner/device that's on the same power circuit for the ground connection.