Black bag air system, black bags come in different designs depending on the application, load and space. They generally sit alongside the OE leaf spring or Torsion Bar. There are three types, Basic consisting of bags, connecting air line and a Schrader Valve. Comfort type adds a compressor and gauges so you can inflate/deflate from the comprt of say, typically a motorhome. The Automatic system is self-levelling and is usually used on mini-buses .