Reverification of Screen Trays for Gilson Testing Screens, Test-Masters®, and Porta-Screens® assures continued reliability for your particle sizing operations. In-service Screen Trays shipped to our Gilson Lab have a specified number of openings measured on an NIST traceable optical comparator. The process is identical to Screen Tray Verification for new units and provides the same measurements and documentation to indicate continued conformance to ASTM E11 or ISO 565/3301-1 Inspection or Calibration Grade requirements. The computerized system provides a Verification Report to document that the cloth still meets Inspection or Calibration Grade requirements to maintain compliance with ASTM or ISO standards. For greater precision or traceable documentation, Compliance Screen Trays can be verified to Inspection or Calibration Grade.