X0508 4 2024-03-18 0 0000036029 FIRST FINANCIAL BANKSHARES INC FFIN 0001243211 DUESER F SCOTT P. O. BOX 701 ABILENE TX 79604-0701 1 1 0 0 Chairman, President and CEO 0 Common Stock 2024-03-18 4 A 0 9814 0.00 A 960879 I By Trust Common Stock 2024-03-18 4 D 0 9814 0.00 D 951065 I By Trust Common Stock 496004 I By Partnership Common Stock 448310 I By Partnership Deferred Stock Units 2024-03-18 4 A 0 9814 D Common Stock 9814 19822 D Represents shares of common stock issued upon the vesting of outstanding performance stock units that were subject to performance criteria other than the issuer's stock price. Represents shares held by several trusts of which Mr. Dueser is trustee, settlor and beneficiary. In connection with the vesting on March 18, 2024, of 9,814 performance stock units previously granted to Mr. Dueser on August 16, 2021, Mr. Dueser's receipt of 9,814 shares of common stock was deferred resulting in Mr. Dueser's receipt instead of 9,814 shares of deferred stock units into the First Financial Bankshares, Inc. Supplemental Executive Retirement Plan, as amended and restated effective July 26, 2022 (the "SERP"). Mr. Dueser is therefore reporting the disposition of 9,814 performance stock units in exchange for an equal number of shares of deferred stock units under the SERP, which are payable upon Mr. Dueser's termination of employment. Represents shares that are owned by a family limited partnership of which Mr. Dueser serves as manager of the general partner and to which he disclaims beneficial ownership with respect to 372,003 shares. This report should not be deemed an admission that Mr. Dueser is the beneficial owner of these shares for purposes of Section 16 or any other purpose. Represents shares that are owned by a family limited partnership of which Mr. Dueser serves as manager of the general partner and to which he disclaims beneficial ownership with respect to 319,636 shares. This report should not be deemed an admission that Mr. Dueser is the beneficial owner of these shares for purposes of Section 16 or any other purpose. By: Michelle S. Hickox Attorney in Fact for F. Scott Dueser 2024-03-20