X0202 SCHEDULE 13G/A 0001172661-26-000935 0000351173 XXXXXXXX LIVE 1 Common stock, par value $0.001 per share 03/31/2026 0001275014 Ultra Clean Holdings, Inc. 90385V107 26462 Corporate Avenue Hayward CA 94545 Rule 13d-1(b) FRONTIER CAPITAL MANAGEMENT CO.,LLC DE 1002952.00 0.00 1787451.00 0.00 1787451.00 N 3.93 IA Ultra Clean Holdings, Inc. 26462 Corporate Avenue Hayward, CA 94545 FRONTIER CAPITAL MANAGEMENT CO., LLC 99 Summer Street Boston, MA 02110 Delaware N IA 1,787,451 3.93% 1,002,952 0 1,787,451 0 N Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. FRONTIER CAPITAL MANAGEMENT CO.,LLC Robert E. Phay 05/15/2026