The National Institute of Standards and Technology (NIST) is seeking potential sources for a high-finesse, dual-wavelength reference cavity system, which is critical for precise thermodynamic temperature measurements. The system must integrate two optical cavities into a single ultra-low expansion (ULE) glass cavity spacer, with specific requirements including a finesse exceeding 100,000 at designated wavelengths and a vacuum housing capable of maintaining pressure below 10^-6 torr. This procurement is essential for advancing measurement standards and ensuring accuracy in scientific research. Interested companies are encouraged to submit their technical capabilities, manufacturing locations, and relevant services to NIST, with responses directed to Elizabeth Timberlake at elizabeth.timberlake@nist.gov or Forest Crumpler at forest.crumpler@nist.gov. This notice is for market research purposes only and does not guarantee future contracts.