Sec Form 4 Filing - Petersen Timothy @ SI-BONE, Inc. - 2018-10-19

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Petersen Timothy 2. Issuer Name and Ticker or Trading Symbol SI-BONE, Inc. [ SIBN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O ARBORETUM VENTURES, 303 DETROIT STREET, SUITE 301 3. Date of Earliest Transaction (MM/DD/YY) 10/19/2018 (Street) ANN ARBOR, MI48104 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 10/19/2018 C 1,495,036 A 1,495,036 I By Arboretum Ventures IV, LP ( 2 ) Common Stock 10/19/2018 P 200,000 A $ 15 1,695,036 I By Arboretum Ventures IV, LP ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series 7 Preferred Stock ( 1 ) 10/19/2018 C 1,495,036 ( 1 ) ( 1 ) Common Stock 1,495,036 ( 1 ) 0 I By Arboretum Ventures IV, LP ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Petersen Timothy C/O ARBORETUM VENTURES 303 DETROIT STREET, SUITE 301 ANN ARBOR, MI48104 X Signatures /s/ Michael A. Pisetsky, Attorney-in-Fact for Timothy B. Petersen 10/19/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Issuer's Series 7 Preferred Stock automatically converted into an equal number of shares of Issuer's common stock immediately upon the closing of the Issuer's initial public offering and has no expiration date. ( 2 )Shares held by Arboretum Ventures IV, LP ("AV IV"). Arboretum Investment Manager IV, LLC ("AIM IV") serves as the general partner of AV IV. Jan Garfinkle, Timothy B. Petersen, a member of the Issuer's board of directors, and Paul McCreadie are managing members of AIM IV and share voting and dispositive power with regard to these shares and therefore each of the foregoing managing members may be deemed to have the same powers with respect to such shares. Mr. Petersen disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest, if any.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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