David S. Winter and David J. Millstone

David S. Winter and David J. Millstone‘s 40 North Management has just filed a Form 13D with the SEC, updating the regulatory body on the latest pertinent information related to its position in Mattress Firm Holding Corp (NASDAQ:MFRM), one of its top stock picks. The activist filing shows that 40 North Management has made several purchases of the company’s shares over the past nine days, amounting to about 450,000 shares, lifting its ownership stake to 3.63 million shares. You can see the latest ownership position in the table below, while the filing is embedded below and on the following pages.

You can access the original SEC filing by clicking here.

Ownership Summary Table

Name Sole Voting Power Shared Voting Power Sole Dispositive Power Shared Dispositive Power Aggregate Amount Owned Power Percent of Class
40 NORTH MANAGEMENT LLC 3,630,262 0 3,630,262 0 3,630,262 9.8%
40 NORTH LATITUDE MASTER FUND LTD. 0 3,630,262 0 3,630,262 3,630,262 9.8%
40 NORTH LATITUDE SPV-B LLC 0 2,465,971 0 2,465,971 2,465,971 6.7%
40 NORTH LATITUDE FUND LP 0 3,630,262 0 3,630,262 3,630,262 9.8%
40 NORTH GP III LLC 0 3,630,262 0 3,630,262 3,630,262 9.8%
DAVID S. WINTER 0 3,630,262 0 3,630,262 3,630,262 9.8%
DAVID J. MILLSTONE 0 3,630,262 0 3,630,262 3,630,262 9.8%
David S. Winter And David J. Millstone
David S. Winter And David J. Millstone
40 North Management

Page 1 of 13 SEC Filing

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Amendment No. 10)*

Under the Securities Exchange Act of
1934

MATTRESS FIRM HOLDING CORP.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

57722W106

(CUSIP Number)

David S. Winter

40 North Management LLC

9 West 57th Street, 30th Floor

New York, New York 10019

(212) 821-1600

(Name, Address and Telephone Number of
Person Authorized to Receive Notices and Communications)

COPIES TO:

Robert W. Downes, Esq.

Sullivan & Cromwell LLP

125 Broad Street

New York, New York 10004-2498

(212) 558-4312

February 17,
2016

(Date of Event which Requires Filing
of this Statement)

If the filing person has previously filed a statement on Schedule
13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e),
240.13d-1(f) or 240.13d-1(g), check the following box. ¨

Note: Schedules filed in paper format shall include a
signed original and five copies of the schedule, including all exhibits. See Rule §240.13d-7 for other parties to whom copies
are to be sent.

* 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 disclosures provided in a prior cover page.

The information required on 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).

Continued on following pages

Page 1 of 13 Pages

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