With catalytic converters being used on new vehicles since 1975, the demand for replacement units has been growing. The high costs of OEM replacements and the subsequent temptation to use substitute pipe or questionable used converters led the Federal Environmental Protection Agency (EPA) to request the industry to develop an “under $100 converter” (1). This paper discusses the need for a market based approach to establishing cost, performance and durability goals for low priced aftermarket catalytic converters. A rationale is suggested for assigning numerical values to these goals. A practical design approach using a radial flow pelletized converter is presented to meet these goals.