A DUPRO is conducted mid-production, typically when 20 to 80% of units have been produced and partially packed. The inspector checks production-line output against your approved specification, identifies emerging defect patterns, and reports while the factory still has time to correct them.
The economics are straightforward: the cost of DUPRO is always less than the cost of a failed FRI. A defect found at DUPRO affects 500 units. The same defect found at FRI affects the entire shipment.