This screw is for the old Gaggia lever group tension springs, as well as the screws for the upper burr on a Rancilio MD-50 grinder, as well as the Simonelli Mythos inner grinder burr screws and the Fiorenzato MC flat burrs.
"TCI" screw stands for "testa con intaglio" or "head with notch".
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WARNING: This product can expose you to chemicals including lead, which are known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information, go to www.p65warnings.ca.gov.