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Exhibit 99.1 Press Release Ultra Clean Reports First Quarter 2021 Financial Results Source : Ultra Clean Holdings , Inc. HAYWARD , Calif . , April 28 , 2021 / PRNewswire / Ultra Clean Holdings , Inc. ( Nasdaq : UCTT ) , today reported its financial results for the first quarter ended March 26 , 2021 . " Accelerating semiconductor demand , together with UCT's ability to execute on a global scale , resulted in another very robust quarter for the company , " said Jim Scholhamer , CEO . " We have strong momentum across the company as our broad portfolio of products and services , including Ham - Let , makes us increasingly relevant and strategic to the success of our customers . Demand for semiconductors has never been higher and we will continue to invest in ways that position UCT to play a larger , more pivotal role in the industry's future . " First Quarter 2021 GAAP Financial Results Total revenue was $ 417.6 million . Products contributed $ 345.6 million and Services added $ 72.0 million . Total gross margin was 20.8 % , operating margin was 9.7 % , and net income was $ 25.0 million or $ 0.62 and $ 0.60 per basic and diluted share . This compares to total revenue of $ 369.6 million , gross margin of 21.0 % , operating margin of 9.0 % , and net income of $ 22.6 million or $ 0.56 and $ 0.55 per basic and diluted share in the prior quarter . First Quarter 2021 Non - GAAP Financial Results On a non - GAAP basis , gross margin was 21.3 % , operating margin was 12.2 % , and net income was $ 38.2 million or $ 0.92 per diluted share . This compares to gross margin of 21.5 % , operating margin of 11.9 % , and net income of $ 33.5 million or $ 0.81 per diluted share in the prior quarter . Second Quarter 2021 Outlook Due to limited visibility resulting from the pandemic , the Company has widened its guidance ranges to reflect the heightened uncertainty in the marketplace . The Company expects revenue in the range of $ 490.0 million to $ 520.0 million and GAAP diluted net income per share to be between $ 0.56 and $ 0.68 . The Company expects non - GAAP diluted net income per share to be between $ 0.90 and $ 1.03 . Conference Call The call will take place at 1:45 p.m. PT and can be accessed by dialing 1-844-826-3034 or 1-412-317-5179 . No passcode is required . A replay of the call will be available by dialing 1-877-344-7529 or 1-412-317-0088 and entering the confirmation code 10154013. The Webcast will be available on the Investor Relations section of the Company's website at http://uct.com/investors/events/ . About Ultra Clean Holdings , Inc. Ultra Clean Holdings , Inc. is a leading developer and supplier of critical subsystems , components and parts , and ultra - high purity cleaning and analytical services primarily for the semiconductor industry . Under its Products division , UCT offers its customers an integrated outsourced solution for major subassemblies , improved design - to - delivery cycle times , design for manufacturability , prototyping , and high - precision manufacturing . Under its Services Division , UCT offers its customers tool chamber parts cleaning and coating , as well as micro - contamination analytical services . Ultra Clean is headquartered in Hayward , California . Additional information is available at www.uct.com . Use of Non - GAAP Measures In addition to providing results that are determined in accordance with Generally Accepted Accounting Principles in the United States of America ( GAAP ) , management uses non - GAAP gross margin , non - GAAP operating margin and non - GAAP net income to evaluate the Company's operating and financial results . We believe the presentation of non - GAAP results is useful to investors for analyzing our core