Book of Numbers is an index of used catalytic converters. Each catalytic converter model has a distinct value based on its combination of Rhodium, Platinum, and Palladium, which filter exhaust. This book is used to establish standard values by offering estimates for the most commonly traded catalytic converters based on year, make, and model. Trade of used catalytic converters is illegal in most of the United States because their disposal is regulated by state emissions laws
