SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. )*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13G

(1)                                 Montreux Equity Partners IV, L.P. (“MEP IV”) is a California limited partnership whose principal business is making investments in the securities of other entities. Montreux IV Associates, L.L.C. (“Associates”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux IV Associates IV, L.L.C. (“Associates IV”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux Equity Management IV, L.L.C. (“MEM IV”) is a California limited liability company, the sole general partner of MEP IV and the manager of Associates and Associates IV. Daniel K. Turner, III is an individual and citizen of the United States of America and sole manager of MEM IV. Each of MEM IV and Mr. Turner disclaim beneficial ownership of such securities, except to the extent of their respective pecuniary interests therein.

(2)                                 Based upon 24,335,690 shares of the Common Stock of the Issuer outstanding as of November 28, 2018 as reported by the Issuer on its Form 10-Q filed with the Securities and Exchange Commission on November 29, 2018.

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SCHEDULE 13G

(1)                                 Montreux Equity Partners IV, L.P. (“MEP IV”) is a California limited partnership whose principal business is making investments in the securities of other entities. Montreux IV Associates, L.L.C. (“Associates”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux IV Associates IV, L.L.C. (“Associates IV”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux Equity Management IV, L.L.C. (“MEM IV”) is a California limited liability company, the sole general partner of MEP IV and the manager of Associates and Associates IV. Daniel K. Turner, III is an individual and citizen of the United States of America and sole manager of MEM IV. Each of MEM IV and Mr. Turner disclaim beneficial ownership of such securities, except to the extent of their respective pecuniary interests therein.

(2)                                 Based upon 24,335,690 shares of the Common Stock of the Issuer outstanding as of November 28, 2018 as reported by the Issuer on its Form 10-Q filed with the Securities and Exchange Commission on November 29, 2018.

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SCHEDULE 13G

(1)                                 Montreux Equity Partners IV, L.P. (“MEP IV”) is a California limited partnership whose principal business is making investments in the securities of other entities. Montreux IV Associates, L.L.C. (“Associates”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux IV Associates IV, L.L.C. (“Associates IV”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux Equity Management IV, L.L.C. (“MEM IV”) is a California limited liability company, the sole general partner of MEP IV and the manager of Associates and Associates IV. Daniel K. Turner, III is an individual and citizen of the United States of America and sole manager of MEM IV. Each of MEM IV and Mr. Turner disclaim beneficial ownership of such securities, except to the extent of their respective pecuniary interests therein.

(2)                                 Based upon 24,335,690 shares of the Common Stock of the Issuer outstanding as of November 28, 2018 as reported by the Issuer on its Form 10-Q filed with the Securities and Exchange Commission on November 29, 2018.

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SCHEDULE 13G

(1)                                 Montreux Equity Partners IV, L.P. (“MEP IV”) is a California limited partnership whose principal business is making investments in the securities of other entities. Montreux IV Associates, L.L.C. (“Associates”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux IV Associates IV, L.L.C. (“Associates IV”) is a California limited liability company whose principal business is making investments in the securities of other entities. Montreux Equity Management IV, L.L.C. (“MEM IV”) is a California limited liability company, the sole general partner of MEP IV and the manager of Associates and Associates IV. Daniel K. Turner, III is an individual and citizen of the United States of America and sole manager of MEM IV. Each of MEM IV and Mr. Turner disclaim beneficial ownership of such securities, except to the extent of their respective pecuniary interests therein.

(2)                                 Based upon 24,335,690 shares of the Common Stock of the Issuer outstanding as of November 28, 2018 as reported by the Issuer on its Form 10-Q filed with the Securities and Exchange Commission on November 29, 2018.

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(a) Amount beneficially owned

(b) Percent of class

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(c)(i) Number of shares to which the person has sole power to vote or direct the vote

(c)(ii) Number of shares to which the person has shared power to vote or direct the vote

(c)(iii) Number of shares to which the person has sole power to dispose or direct the disposition of

(c)(iv) Number of shares to which the person has shared power to dispose or direct the disposition of

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SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: February 14, 2019

Signature Page to Schedule 13G

Issuer: SI-BONE, Inc.

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EXHIBIT INDEX

Exhibit I — Joint Filing Agreement

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EXHIBIT I

Joint Filing Agreement

THIS JOINT FILING AGREEMENT is entered into as of February 14, 2019, by and among the parties signatories hereto. The undersigned hereby agree that the Statement on Schedule 13G with respect to the shares of Common Stock, par value $0.0001 per share, of SI-BONE, Inc. is, and any amendment thereafter signed by each of the undersigned shall be, filed on behalf of each undersigned pursuant to and in accordance with the provisions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended.

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