ISO-K and ISO-F Sight Glass Windows
Select Stock Configurations Below
  • ISO-K AND ISO-F (also known as LF, LFB, MF) - flanged vacuum sight glasses
  • Exhibits no outgassing or contamination of most systems*
  • Long working life
  • No maintenance required
  • Tested to high safety factor to insure safety & reliability
  • Exceeds all industry and MIL standards
  • Engineered, Manufactured and tested at the Rayotek U.S. facility

ISO-K AND ISO-F (also known as LF, LFB, MF) sight windows are used for clean, ultra high vacuum and low pressure applications. Designed specifically for applications where cleanliness, chemical resistance and/or process control are critical. The window material is fused or bonded to a stainless steel housing forming a hermetically sealed single-piece part. The advantage of this construction is a simple, clean, easy to install sight window.

ISO-F flanges are designed to be attached with bolts.
ISO-K flanges are designed similar to KF flanges in that they are attached with ISO-K clamps (not sold with sight window).

Click Configuration for specifications and part numbers.

Temperature Range
General purpose indicator & observation, NACE MR0175/ISO15156 compliant
0 Kelvin - 400C
General purpose flat window for imaging and precision optical measurement
0 Kelvin - 200C
Optical quality, extreme scratch and chemical resistance for UV, visible & IR viewing
0 Kelvin - 200C


  • Semiconductor processing equipment
  • Pharmaceutical & chemical processing
  • Food processing & sanitary applications
  • Precision observation & measurement systems
  • Cryogenic & super critical applications
  • Ultra high vacuum equipment for research & industry

Rayotek sight windows can transmit a broad range of wavelengths and are capable of operating under extreme temperature, pressure, chemical and mechanical conditions. The selection of window and housing materials will determine capabilities.

† Alternative materials are available upon request including, but not limited to:
        Housing: duplex, aluminum, Monel, Inconel, plastics and alumina
        Window: borosilicate (Pyrex®), diamond, Zinc Selenide, fused silica, germanium, MgF2, silicon and YAG

*  For systems where purity & cleanliness are critical, Rayotek recommends testing the Sight Window for specific chemical compatibility.
    Call for information.

** Typical leak rate is 10-8 bar-CC/sec. for air at 22C. Actual leak rate TBD based on window size and maximum operating temperature.
    Call for information.

Contact Us with questions or to discuss your requirements and we'll be happy to help