Philmore 64-4005 Low level RCA Ground loop Isolator.
The Philmore ground loop isolator is a low level filter which isolates the ground between amplifier and radio. It eliminates the ground path which can cause alternator whine and ignition pop.
The 64-4005 is equipped with two RCA Females for interconnection with cable adaptor / components. The all metal case will give additional shielding and create better isolation between the head unit and amplifier.