Skyline Venture Partners V SC 13G SI-BONE, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1 (b),

(c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO 13d-2 (b)

(Amendment No.     )*

SI-BONE, INC.

(Name of Issuer)

COMMON STOCK, PAR VALUE $0.0001 PER SHARE

(Title of Class of Securities)

825704109

(CUSIP Number)

DECEMBER 31, 2018

(Date of Event Which Requires Filing of this Statement)

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

o Rule 13d-1(b)

o Rule 13d-1(c)

x Rule 13d-1(d)

*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).

CUSIP No. 825704109
	1.	Name of Reporting Persons Skyline Venture Partners V, L.P.
	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)		o
		(b)		x (1)
	3.	SEC Use Only
	4.	Citizenship or Place of Organization Delaware, United States of America
Number of Shares Beneficially Owned by Each Reporting Person With:			5.		Sole Voting Power 0
			6.		Shared Voting Power 4,419,985 (2)
			7.		Sole Dispositive Power 0
			8.		Shared Dispositive Power 4,419,985 (2)
	9.	Aggregate Amount Beneficially Owned by Each Reporting Person 4,419,985 (2)
	10.	Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)
	11.	Percent of Class Represented by Amount in Row (9) 18.2% (3)
	12.	Type of Reporting Person (See Instructions) PN

(1)  This Schedule 13G is filed by Skyline Venture Partners V, L.P. (“SVP V”), Skyline Venture Management V, LLC (“SVM V”) , John G. Freund (“Freund”) and Yasunori Kaneko (“Kaneko” and together with SVP V, SVM V and Freund the “Skyline Entities”).  The Skyline Entities expressly disclaim status as a “group” for purposes of this Schedule 13G.

(2)  The shares are held by SVP V.  SVM V is the sole general partner of SVP V.  Freund and Kaneko are managing directors of SVM V and share voting and dispositive power over the shares held by the SVP V.

(3)  This percentage is calculated based upon 24,335,690 shares of the Issuer’s common stock outstanding as of November 28, 2018 as set forth in the Issuers most recent 10-Q, filed with the Securities and Exchange Commission on November 29, 2018.

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CUSIP No. 825704109
	1.	Name of Reporting Persons Skyline Venture Management V, LLC
	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)		o
		(b)		x (1)
	3.	SEC Use Only
	4.	Citizenship or Place of Organization Delaware, United States of America
Number of Shares Beneficially Owned by Each Reporting Person With:			5.		Sole Voting Power 0
			6.		Shared Voting Power 4,419,985 (2)
			7.		Sole Dispositive Power 0
			8.		Shared Dispositive Power 4,419,985 (2)
	9.	Aggregate Amount Beneficially Owned by Each Reporting Person 4,419,985 (2)
	10.	Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)
	11.	Percent of Class Represented by Amount in Row (9) 18.2% (3)
	12.	Type of Reporting Person (See Instructions) OO

(1)  This Schedule 13G is filed by Skyline Venture Partners V, L.P. (“SVP V”), Skyline Venture Management V, LLC (“SVM V”) , John G. Freund (“Freund”) and Yasunori Kaneko (“Kaneko” and together with SVP V, SVM V and Freund the “Skyline Entities”).  The Skyline Entities expressly disclaim status as a “group” for purposes of this Schedule 13G.

(2)  The shares are held by SVP V.  SVM V is the sole general partner of SVP V.  Freund and Kaneko are managing directors of SVM V and share voting and dispositive power over the shares held by the SVP V.

(3)  This percentage is calculated based upon 24,335,690 shares of the Issuer’s common stock outstanding as of November 28, 2018 as set forth in the Issuers most recent 10-Q, filed with the Securities and Exchange Commission on November 29, 2018.

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CUSIP No. 825704109
	1.	Name of Reporting Persons Yasunori Kaneko
	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)		o
		(b)		x (1)
	3.	SEC Use Only
	4.	Citizenship or Place of Organization California, United States of America
Number of Shares Beneficially Owned by Each Reporting Person With:			5.		Sole Voting Power 0
			6.		Shared Voting Power 4,419,985 (2)
			7.		Sole Dispositive Power 0
			8.		Shared Dispositive Power 4,419,985 (2)
	9.	Aggregate Amount Beneficially Owned by Each Reporting Person 4,419,985 (2)
	10.	Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)
	11.	Percent of Class Represented by Amount in Row (9) 18.2% (3)
	12.	Type of Reporting Person (See Instructions) IN

(1) This Schedule 13G is filed by Skyline Venture Partners V, L.P. (“SVP V”), Skyline Venture Management V, LLC (“SVM V”) , John G. Freund (“Freund”) and Yasunori Kaneko (“Kaneko” and together with SVP V, SVM V and Freund the “Skyline Entities”).  The Skyline Entities expressly disclaim status as a “group” for purposes of this Schedule 13G.

(2)  The shares are held by SVP V.  SVM V is the sole general partner of SVP V.  Freund and Kaneko are managing directors of SVM V and share voting and dispositive power over the shares held by the SVP V.

(3)  This percentage is calculated based upon 24,335,690 shares of the Issuer’s common stock outstanding as of November 28, 2018 as set forth in the Issuers most recent 10-Q, filed with the Securities and Exchange Commission on November 29, 2018.

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CUSIP No. 825704109
	1.	Name of Reporting Persons John G. Freund
	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)		o
		(b)		x (1)
	3.	SEC Use Only
	4.	Citizenship or Place of Organization California, United States of America
Number of Shares Beneficially Owned by Each Reporting Person With:			5.		Sole Voting Power 0
			6.		Shared Voting Power 4,419,985 (2)
			7.		Sole Dispositive Power 0
			8.		Shared Dispositive Power 4,419,985 (2)
	9.	Aggregate Amount Beneficially Owned by Each Reporting Person 4,419,985 (2)
	10.	Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)
	11.	Percent of Class Represented by Amount in Row (9) 18.2% (3)
	12.	Type of Reporting Person (See Instructions) IN

(1) This Schedule 13G is filed by Skyline Venture Partners V, L.P. (“SVP V”), Skyline Venture Management V, LLC (“SVM V”) , John G. Freund (“Freund”) and Yasunori Kaneko (“Kaneko” and together with SVP V, SVM V and Freund the “Skyline Entities”).  The Skyline Entities expressly disclaim status as a “group” for purposes of this Schedule 13G.

(2)  The shares are held by SVP V.  SVM V is the sole general partner of SVP V.  Freund and Kaneko are managing directors of SVM V and share voting and dispositive power over the shares held by the SVP V.

(3)  This percentage is calculated based upon 24,335,690 shares of the Issuer’s common stock outstanding as of November 28, 2018 as set forth in the Issuers most recent 10-Q, filed with the Securities and Exchange Commission on November 29, 2018.

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CUSIP No.  825704109

Introductory Note: This Statement on Schedule 13G is filed on behalf of Skyline Venture Partners V, L.P., a limited partnership organized under the laws of the State of Delaware (“SVP V”), Skyline Venture Management V, LLC, a limited liability company organized under the laws of the State of Delaware (“SVP V”),  John G. Freund (“Freund”) and Yasunori Kaneko (“Kaneko”, and together with SVP V, SVM V and Freund, the “Skyline Entities”) in respect of shares of Common Stock of SI-BONE, Inc.

Item 1(a)	Name of Issuer SI-BONE, Inc.
Item 1(b)	Address of Issuer’s Principal Executive Offices 471 El Camino Real, Suite 101 Santa Clara, CA  95050
Item 2(a)	Name of Person Filing Skyline Venture Partners V, L.P. Skyline Venture Management V, LLC John G. Freund Yasunori Kaneko
Item 2(b)	Address of Principal Business Office or, if none, Residence 525 University Avenue, Suite 1350 Palo Alto, CA 94301
Item 2(c)	Citizenship SVP V is a limited partnership organized in the State of Delaware.  SVM V is a limited liability company organized in the State of Delaware.  Freund and Kaneko are individuals residing in California.
Item 2(d)	Title of Class of Securities Common Stock
Item 2(e)	CUSIP Number 825704109
Item 3	Not applicable.

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CUSIP No.  825704109

Item 4 Ownership

Skyline Entity	Shares Held Directly	Sole  Voting  Power	Shared  Voting  Power	Sole  Dispositive  Power	Shared  Dispositive  Power	Beneficial  Ownership	Percentage  of Class (2)
Skyline Venture Partners V, L.P. (1)	4,419,985	0	4,419,985	0	4,419,985	4,419,985	18.2	%
Skyline Venture Management V, LLC (1)	0	0	4,419,985	0	4,419,985	4,419,985	18.2	%
Yasunori Kaneko (1)	0	0	4,419,985	0	4,419,985	4,419,985	18.2	%
John G. Freund (1)	0	0	4,419,985	0	4,419,985	4,419,985	18.2	%

(1)  The shares are held by SVP V.  SVM V is the sole general partner of SVP V.  Freund and Kaneko are managing directors of SVM V and share voting and dispositive power over the shares held by the SVP V.

(2)  This percentage is calculated based upon 24,335,690 shares of the Issuer’s common stock outstanding as of November 28, 2018 as set forth in the Issuers most recent 10-Q, filed with the Securities and Exchange Commission on November 29, 2018.

Item 5	Ownership of Five Percent or Less of a Class
If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following   o.
Item 6	Ownership of More than Five Percent of Another Person
Not applicable.
Item 7	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company
Not applicable.
Item 8	Identification and Classification of Members of the Group
Not applicable.
Item 9	Notice of Dissolution of Group
Not applicable.

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CUSIP No.  825704109

Item 10	Certification
Not applicable.

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.

February 14, 2019	SKYLINE VENTURE PARTNERS V, L.P.
	BY:	SKYLINE VENTURE MANAGEMENT V, LLC
	ITS:	GENERAL PARTNER
	By:	/s/ Kerensa Kenny as attorney-in-fact
		John G. Freund
		Managing Director
	SKYLINE VENTURE MANAGEMENT V, LLC
	By:	/s/ Kerensa Kenny as attorney-in-fact
		John G. Freund
		Managing Member
		/s/ Kerensa Kenny as attorney-in-fact
		YASUNORI KANEKO
		/s/ Kerensa Kenny as attorney-in-fact
		JOHN G. FREUND

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CUSIP No.  825704109

EXHIBIT INDEX

Exhibit No.
99.1	Agreement pursuant to 13d-1(k)(1) among Skyline Venture Partners V, L.P., Skyline Venture Management V, LLC John G. Freund and Yasunori Kaneko.

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