O'Reilly Automotive operates one of the largest auto parts retail chains in the United States, selling replacement parts, tools and accessories to both do-it-yourself customers and professional repair shops. Its dual customer base gives O'Reilly two distinct revenue streams: retail sales to individual car owners doing their own repairs, and a larger commercial business supplying parts to auto repair shops and other professional installers. Demand for auto parts tends to hold up well during economic downturns, since people often repair aging vehicles rather than buying new ones when budgets are tight, giving the business a somewhat defensive characteristic. O'Reilly has built an extensive distribution network of regional warehouses that let its stores offer same-day or next-day availability on a wide range of parts, a logistics advantage that smaller competitors struggle to match.