O'ReillyAutoParts is the third largest auto parts retailer in the US. The auto parts industry is mature but growing slowly as vehicles age and miles driven increase. The industry is becoming more oligopolistic as the top 4 firms gain market share. O'Reilly has been able to increase its gross margin through economies of scale achieved via acquisitions and new store openings, bringing its store count to over 4,500. The company focuses on DIY and professional installation customers by ensuring fast delivery of parts, including hard-to-find items, and providing extensive training to technicians.