These ISO Glass Viewport flanges follow International Standards Organization (ISO) standards and have a flange size of NW-63. The viewport uses borosilicate glass NW ISO in a one-piece assembly. This viewport replaces a blank off cap, includes a Fluorocarbon Rubber O-Ring and uses a double claw clamp for sealing. ISO flanged vacuum fittings are commonly used to build process vacuum plumbing and systems for industrial applications. The ISO standard sizes for large flanges are NW-63, NW-80, NW-100, NW-160, NW-200, NW-250, NW-320, NW-400, NW-500, NW-630. These vacuum fittings are made of aluminum 6082. For complete specs see info brochure to the left at Downloads