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Table of Contents ( Mark One ) UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 . OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Commission file number 001-38066 Delaware ( State or Other Jurisdiction of Incorporation or Organization ) Select Energy Services , Inc. ( Exact name of registrant as specified in its charter ) 1233 W. Loop South , Suite 1400 Houston , Texas ( Address of Principal Executive Offices ) to Title of each class Class A common stock , par value $ 0.01 per share 81-4561945 ( I.R.S. Employer Identification No. ) Registrant's telephone number , including area code ( 713 ) 235-9500 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) WTTR Securities registered pursuant to Section 12 ( g ) of the Act : NONE Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No ✔ Large Accelerated Filer Non - accelerated Filer 77027 ( Zip Code ) Name of each exchange on which registered New York Stock Exchange Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes No ✓ Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes ✔ No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , ” “ smaller reporting company ” and “ emerging growth company " in Rule 12b - 2 of the Exchange Act . Accelerated Filer Smaller reporting company Emerging growth company DOO If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Indicate by check mark whether the registrant is a shell company ( as defined by Rule 12b - 2 of the Act ) . Yes No ✔ Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . The aggregate market value of the voting and non - voting common stock held by non - affiliates of the registrant computed as of June 30 , 2020 ( the last business day of the registrant's most recent completed second fiscal quarter ) based on the closing price of the Class A common stock on the New York Stock Exchange was $ 284.2 million . There were 86,437,630 and 16,221,101 shares of the registrant's Class A and Class B common stock , respectively , outstanding as of February 22 , 2021 . Documents Incorporated by Reference : Portions of the registrant's definitive proxy statement for the 2021 annual meeting of stockholders , to be filed no later than 120 days after the end of the fiscal year , are incorporated by reference into Part III of this Annual Report on Form 10 - K .