12 components of exhaust gas systems for land, air and water vehicle engines, namely, catalytic converters, valves, silencers, bafflers, mufflers, manifolds, exhaust pipes and tubes, tail pipes, catalyst installation kits, hangers, clamps, pipe connectors, installation kits for pre-heater pipes, installation kits for front pipes, installation kits for silencers; exhaust gas systems comprised of some or all of the foregoing components