FU for short, FLI Underground is all about edgy products that are perfect for creating a quality car audio install on a budget. The FLI Underground range includes everything you need to upgrade your audio install with Coaxial & Component Speakers, Subwoofers, Amplifiers and Active Bass Enclosures. With easy fitment and amazing reliability, FLI Underground is bringing car audio to the masses and to OnlineCarStereo.