The National Institute of Standards and Technology (NIST) is conducting market research to identify vendors capable of supplying a replacement high-performance cesium beam tube for a 5071A frequency standard. This is a sources sought notice, not a solicitation, and no contract will be awarded from this announcement. Responses must include the country of manufacture, capability statements limited to four pages, and typical lead time for delivery. The government will use the results to determine if a small business set-aside is possible, with a NAICS code of 334519 and a 600-employee size standard. No budget or performance location is specified.