This is a sole-source upgrade requirement for an existing Zeiss Serial Block Face Scanning Electron Microscope (SBF-SEM) at the National Institute of Biomedical Imaging and Bioengineering, intended to be awarded to Carl Zeiss as the original manufacturer. The justification cites proprietary technology, system compatibility, factory calibration, warranty preservation, lack of equivalent alternatives, and research continuity as reasons only Carl Zeiss can perform the upgrade. No budget amount or performance location is specified. Interested responsible sources—including small businesses and various socioeconomic categories—may submit a capability statement to demonstrate their ability to satisfy the requirement, which will be evaluated to determine whether competition is feasible. The government anticipates award shortly after the submission deadline unless an alternative capable source is identified.