Product quality appraisal has three characteristics:
1. In case of product quality dispute, there will be no product quality appraisal without dispute.
2. The product status of quality appraisal is mostly used, worn, damaged and out of performance, and it is impossible to explain the causes of product quality problems and who caused them. Therefore, product quality appraisal is the "diagnosis" work of product quality appraisal.
3. The technical work of quality appraisal shall be carried out by technical experts organized by the quality appraisal unit, and the expert group shall investigate, analyze and judge the products and issue a quality appraisal report.