Acceptance of undertaking in lieu of bond restored temporarily; importers/exporters must later replace undertakings with proper bonds. Restoration of the facility for acceptance of undertaking in lieu of bond allows importers/exporters to furnish an undertaking instead of a formal bond for Customs clearance during the temporary revival; such undertakings must be replaced by proper bonds within the prescribed replacement period, and the terms and conditions of the earlier circulars (as amended) continue to apply.