The article explores how product quality is defined in markets. It challenges the idea that only one characteristic matters in quality differentiation. The researchers found that in some cases, a company can lead in two quality attributes, while in others, there is cross leadership where each firm excels in one characteristic. They also looked at cost complementarities and discussed how this affects quality standards, perception biases, and taxes on quality products. This study suggests that traditional models may not fully capture the complexity of quality differentiation in markets.