No universal duration establishes the classification. Explain the actual special or advanced knowledge and the evidence supporting it.
Use time as context rather than the conclusion
Identify what was learned, how it was applied and why it matters to the proposed duties. A long period may include ordinary work or unrelated training. The complete knowledge and transfer requirements need assessment.
Specialized knowledge is knowledge of the petitioning organization's own product, service, research, equipment, techniques, management or other interests and its application in international markets, or an advanced level of knowledge of the company's processes and procedures. Requests for evidence in L-1B cases almost always ask the same things: what exactly the knowledge is, how it differs from general industry skill, how many people hold it, and why the U.S. entity needs it. The workflow manual — the extraction rules, validation steps, scoring thresholds and quality gates as the company actually applies them — can make the knowledge concrete and show how it relates to the organization rather than general industry practice. Describe the employee’s actual command of relevant company methods, exceptions and applications; familiarity with a general standard or a labour shortage does not alone establish the classification.