X0508 4 2025-12-02 0001018963 ATI INC ATI 0001572385 WETHERBEE ROBERT S 2021 MCKINNEY AVENUE SUITE 1100 DALLAS TX 75201 true true false false Executive Chairman true Common Stock, par value $0.10 per share 2025-12-18 4 S false 6507 108.86 D 180031.3409 D Common Stock, par value $0.10 per share 2025-12-18 4 S false 47355 109.57 D 132676.3409 D Common Stock, par value $0.10 per share 2025-12-18 4 S false 6158 110.34 A 126518.3409 D Shares sold pursuant to a 10b5-1 Trading Plan dated August 15, 2025, entered into for personal tax and estate planning purposes. The price reported is a weighted average price. The shares were sold in multiple transactions at prices ranging from $108.18 to to $109.17. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the U.S. Securities and Exchange Commission (the "SEC"), upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. The shares were sold in multiple transactions at prices ranging from $109.18 to to $110.17. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. The shares were sold in multiple transactions at prices ranging from $110.18 to to $110.67. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. /s/ Amanda J. Skov, Attorney-in-Fact for Robert S. Wetherbee 2025-12-19