Firms applying to use self-prepared general mechanical seals shall submit to the competent field Customs an application form for certification of the usage of self-prepared general mechanical seals and an affidavit of confidentiality with both stamps of the corporate and the responsible person of the firm as well as the documents and materials listed in the application form. The firm shall use the self-prepared seals only after receiving approval from Customs.The listed categories and the criteria for certification of self-prepared general mechanical seals are prescribed in the appended Table 2.Table 2：Criteria for the Performance of General Mechanical Seals.PDF