Excessive customer concentration is one of the most common hidden risks in small and medium-sized manufacturing businesses. When a single customer represents over 40% of revenue, any reduction in orders due to the customer's strategic shift, market decline, or switch to alternative suppliers can result in the loss of the majority of income in a short period, leaving insufficient buffer time for adjustment. Assessment should be approached from two angles: First, regularly calculate the combined percentage of revenue from the top three customers and set alert thresholds (for example, no single customer should exceed 30% of revenue). Second, examine whether these customers operate in related industries, regions, or have similar procurement cycles. If three major customers are all from the same industry, customer diversification alone does not address systemic risk. To genuinely reduce dependency, you need to simultaneously develop small and medium-sized customers, expand into different geographic markets, and set new customer development as a quarterly metric rather than waiting until a major customer cuts orders before taking action.