Optical Filter, Visible Absorbing, 25.4 mm Diameter, Hoya U-340 Glass

The FSR-U340 Visible Absorbing Filter is a 25.4 mm diameter dark glass optical filter that passes UV and absorbs visible wavelengths made of Hoya U-340 filter glass.  These filters are precision polished for demanding research or OEM applications and are ideal for extraction of UV wavelengths.

Warning - this filter is extremely susceptible to high humidity. The filter will absorb moisture, and discoloration may happen.  Please store this in a low humidity environment. We offer the FSR-U340-C , a coated version of this filter for humid environments. It prevents moisture from contaminating filter material, preventing stains, discoloration, and contamination. It also has 3% increase of transmission compared to uncoated version.