X0609 4 2026-09-16 0 0001039399 FORMFACTOR INC FORM 0001590177 SLESSOR MIKE false 7005 SOUTHFRONT ROAD LIVERMORE CA 94551 1 1 0 0 CEO 1 Common Stock 2026-09-16 4 S 0 8737 104.26 D 475467 D Common Stock 2026-09-16 4 S 0 7773 105.12 D 467694 D Common Stock 2026-09-16 4 S 0 1000 105.80 D 466694 D The reported sale of shares occurred automatically pursuant to a Rule 10b5-1 trading plan adopted on August 19, 2025. Price represents the weighted average sale price for the transaction reported. Price range of shares sold is $103.65 through $104.63. Reporting person undertakes to provide upon request by the SEC staff or a security holder of the Issuer, full information regarding the number of shares sold at each separate price. Price represents the weighted average sale price for the transaction reported. Price range of shares sold is $104.66 through $105.615. Reporting person undertakes to provide upon request by the SEC staff or a security holder of the Issuer, full information regarding the number of shares sold at each separate price. /s/ Stan Finkelstein, Attorney-in-fact for Mike Slessor 2026-09-17