There’s no such thing as a real catalytic converter cleaner—not for a cat still on the vehicle anyway—and we would never offer a gimmicky product that didn’t do what it said. Catalytic converters are “self-cleaning” under proper operating conditions and should last the life of the car. If the “guts” are physically intact and there’s just some build up on the catalysts, then running a good fuel system cleaner like part #2616 and making sure the engine is properly tuned—clean injectors, valves, and plugs, good plug wires, factory timing, etc.—can help dramatically. Doing this idealizes or “fixes” the combustion byproducts and allows the catalytic converter to start burning or “shaking off” deposits and reactivating passivated catalytic sites that had gone dormant from buildup.