Research Electro Optics, Inc. (REO) offers air-spaced etalons that feature industry-leading precision together with proven volume manufacturing and state of the art functional metrology. Our proprietary adhesive-free bonding process ensures that our open frame and hermetically sealed air-spaced etalons will exceed all Telcordia requirements for durability and reliability. Available with any combination of reflectivities, in Fabry-Perot or GT configuration, REO's etalons have many applications including precision wavelength locking, interleaving, and dispersion compensation. Our etalons are manufactured to have a transmission or reflection peak or edge at a specified frequency, with a specified Free Spectral Range, at a specified incident angle. REO's hermetic etalons have guaranteed ultra-low temperature drift.