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 RULE 13d-2(b)
(AMENDMENT NO. 6)
MKS Instruments, Inc.
(Name of Issuer)
Common Stock
(Title of Class of Securities)
55306N 10 4
(CUSIP Number)
December 31, 2005
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:
[ ] Rule 13d-1(b)
[ ] Rule 13d-1(c)
[X] Rule 13d-1(d)
CUSIP No. 55306N 10 4 13G Page 2 of Page 6
--------------------------------------------------------------------------------
1 NAMES OF REPORTING PERSONS.
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
John R. Bertucci
--------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ]
(b) [ ]
Not Applicable
--------------------------------------------------------------------------------
3 SEC USE ONLY
--------------------------------------------------------------------------------
4 CITIZENSHIP OR PLACE OF ORGANIZATION
United States
--------------------------------------------------------------------------------
5 SOLE VOTING POWER
0
-----------------------------------------------------------------
NUMBER OF 6 SHARED VOTING POWER
SHARES
BENEFICIALLY 4,677,882(1)
OWNED BY -----------------------------------------------------------------
EACH 7 SOLE DISPOSITIVE POWER
REPORTING
PERSON WITH 4,677,882(1)
-----------------------------------------------------------------
8 SHARED DISPOSITIVE POWER
0
--------------------------------------------------------------------------------
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
4,677,882(1)
--------------------------------------------------------------------------------
10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*
Not Applicable
--------------------------------------------------------------------------------
11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
8.6%
--------------------------------------------------------------------------------
12 TYPE OF REPORTING PERSON*
IN
--------------------------------------------------------------------------------
* See Instructions before filling out
----------
(1) INCLUDES, PURSUANT TO RULE 13D-3, 16,302 SHARES SUBJECT TO OPTIONS
EXERCISABLE WITHIN 60 DAYS OF DECEMBER 31, 2005. EXCLUDES, PURSUANT TO RULE
13D-4, 4,546,784 SHARES BENEFICIALLY OWNED BY CLAIRE R. BERTUCCI, MR.
BERTUCCI'S SPOUSE, WITH RESPECT TO WHICH MR. BERTUCCI DISCLAIMS BENEFICIAL
OWNERSHIP.
CUSIP No. 55306N 10 4 13G Page 3 of Page 6
Item 1(a). Name of Issuer:
MKS Instruments, Inc.
Item 1(b). Address of Issuer's Principal Executive Offices:
90 Industrial Way
Wilmington, MA 01887
Item 2(a). Name of Person Filing:
John R. Bertucci
Item 2(b). Address of Principal Business Office or, if None, Residence:
The address of the reporting persons is:
c/o MKS Instruments, Inc.
90 Industrial Way
Wilmington, MA 01887
Item 2(c). Citizenship:
Mr. Bertucci is a citizen of the United States.
Item 2(d). Title of Class of Securities:
Common Stock, no par value per share.
Item 2(e). CUSIP Number:
CUSIP No. 55306N 10 4
Item 3. If This Statement is Filed Pursuant to Rule 13d-1(b), or 13d-2(b)
or (c), Check Whether the Person Filing is a: Not Applicable.
(a) [ ] Broker or dealer registered under Section 15 of the
Exchange Act.
(b) [ ] Bank as defined in Section 3(a)(6) of the Exchange Act.
(c) [ ] Insurance company as defined in Section 3(a)(19) of the
Exchange Act.
(d) [ ] Investment company registered under Section 8 of the
Investment Company Act.
CUSIP No. 55306N 10 4 13G Page 4 of Page 6
(e) [ ] An investment adviser in accordance with Rule
13d-1(b)(1)(ii)(E);
(f) [ ] An employee benefit plan or endowment fund in
accordance with Rule 13d-1(b)(1)(ii)(F);
(g) [ ] A parent holding company or control person in
accordance with Rule 13d-1(b)(1)(ii)(G);
(h) [ ] A savings association as defined in Section 3(b) of the
Federal Deposit Insurance Act;
(i) [ ] A church plan that is excluded from the definition of
an investment company under Section 3(c)(14) of the
Investment Company Act;
(j) [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J).
Item 4. Ownership:
The filing of this statement shall not be construed as an admission
that the reporting person is, for any purpose other than Section
13(d) or 13(g) of the Act, the beneficial owner of any securities
covered under this Statement.
(a) Amount Beneficially Owned by John R. Bertucci: 4,677,882
shares(2)
(b) Percent of Class: 8.6%
(c) Number of Shares as to which John R. Bertucci has:
(i) Sole power to vote or to direct the vote: 0 shares
(ii) Shared power to vote or to direct the vote: 4,677,882
shares(2)
(iii) Sole power to dispose or to direct the disposition of:
4,677,882(2) shares
(iv) Shared power to dispose or to direct the disposition of:
0 shares
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 5% of the class of securities, check the
following: [ ].
----------
(2) INCLUDES, PURSUANT TO RULE 13D-3, 16,302 SHARES SUBJECT TO OPTIONS
EXERCISABLE WITHIN 60 DAYS OF DECEMBER 31, 2005. EXCLUDES, PURSUANT TO RULE
13D-4, 4,546,784 SHARES BENEFICIALLY OWNED BY CLAIRE R. BERTUCCI, MR.
BERTUCCI'S SPOUSE, WITH RESPECT TO WHICH MR. BERTUCCI DISCLAIMS BENEFICIAL
OWNERSHIP.
CUSIP No. 55306N 10 4 13G Page 5 of Page 6
Item 6. Ownership of More than Five Percent on Behalf of Another Person.
250,000 shares reported by Mr. Bertucci are held by Robinson Hill
LP ("Robinson"). Certain limited partners, along with the general
partner, of which Mr. Bertucci is the managing member, of Robinson,
have the right to receive dividends from, or the proceeds from the
sale of such securities.
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
Item 10. Certification.
Not applicable
CUSIP No. 55306N 10 4 13G Page 6 of Page 6
SIGNATURES
After reasonable inquiry and to the best of the knowledge and belief of
each of the undersigned, each of the undersigned hereby certifies that the
information set forth in this statement is true, complete and correct.
Dated: February 8, 2006
/s/ John R. Bertucci
----------------------------------------
John R. Bertucci