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For STEM OPT Extension, use the code (c)(3)(C) for item 2127.
For more information, refer to the USCIS website Optional Practical Training Extension for STEM Students (STEM OPT).
USCIS also provides instructions for Form I-765 and an Optional Checklist for Form I-765 (c)(3)(C) for students applying for the STEM OPT Extension and form filing tips. See pages 19-20 in Form I-765 Instructions for how to assemble your documents in the correct order.
Refer to the STEM OPT Application Checklist of Required Documentation for the list of items to include in your application.
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