Viking Inspection Ports have large finger grips on the lids for easy access and feature threaded screw in lids and rubber O-rings for a water-tight seal. The Viking Port's unique design integrates the O-Ring into the rim, making it nearly impossible for the O-Ring to fall out. These inspection ports are available in ABS Plastic or Polypropylene which is acetone resistant, (clear centers in ABS only.) Made in the US to imperial (inches) standards. Use the following chart to determine the appropriate APS part number for your Inspection Port or Bag requirement.