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( 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 001-38701 SI - BONE , Inc. ( Exact name of Registrant as specified in its Charter ) Delaware ( State or other jurisdiction of incorporation or organization ) TO 471 El Camino Real , Suite 101 , Santa Clara , California 95050 ( Address of principal executive offices including zip code ) Registrant's telephone number , including area code : ( 408 ) 207-0700 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) . SIBN Large accelerated filer Smaller reporting company 26-2216351 ( I.R.S. Employer Identification No. ) Title of each class Common Stock , par value $ 0.0001 per share Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the Registrant is a well - known seasoned issuer , defined in Rule 405 of the Securities Act . Yes No x Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . Yes No x 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 x No Name of each exchange on which registered The Nasdaq Global Market 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 x 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 : □ 区 Accelerated filer Emerging growth company 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 7 ( a ) ( 2 ) ( B ) of the Securities Act . □ Non - accelerated filer 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 . Indicate by check mark whether the Registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes No x The aggregate market value of the shares of common stock held by non - affiliates of the registrant as of June 30 , 2020 , the last business day of the registrant's most recently completed second fiscal quarter , was approximately $ 394.1 million , calculated based on the closing price of the registrant's common stock as reported by the Nasdaq Global Market . Shares of common stock held by each officer and director , and each entity affiliated with a director , have been excluded in that such persons may be deemed to be affiliates . This determination of affiliate status is not a conclusive determination for other purposes . The number of shares of Registrant's Common Stock outstanding as of March 5 , 2021 was 32,727,666 shares . DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant's Definitive Proxy Statement relating to the Annual Meeting of Shareholders , which will be filed with the Securities and Exchange Commission within 120 days after the end of the Registrant's fiscal year ended December 31 , 2020 , are incorporated by reference into Part III of this Report .