rockford fosgate rfk-hdrk complete amplifier installation kit for 1998+ harley davidson road king motorcycles rockford fosgate the road king kits are designed to deliver an exceptional sound experience while retaining as much interior bag space as possible. the rfk-hdrk amplifier mounting kit is designed for use with the rockford fosgate power tm400x4ad 400-watt amplifier (sold separately) and is supplied with the complete plug-and-play wiring harness. designed for use with 1998-current harley-davidson road king motorcycles.