MKS INC — Director's Dealing 2016

May 5, 2016

SEC Form 3 — Initial Statement of Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2016-05-02

Reporting Person: Werth Dennis L (Sr. VP, Business Units)

Holdings (Derivative)

Security	Exercise Price	Expiration	Underlying	Shares	Ownership
Stock Appreciation Right	$20.32	2017-03-31	Common Stock (5838)		Direct
Stock Appreciation Right	$27.79	2018-05-17	Common Stock (4199)		Direct
Stock Appreciation Right	$27.89	2019-04-12	Common Stock (5911)		Direct
Stock Appreciation Right	$22.39	2020-05-20	Common Stock (10313)		Direct
Restricted Stock Unit	$		Common Stock (2952)		Direct
Stock Appreciation Right	$29.80	2021-05-19	Common Stock (8858)		Direct
Restricted Stock Unit	$		Common Stock (4911)		Direct
Stock Appreciation Right	$31.13	2022-05-19	Common Stock (7366)		Direct

Footnotes

F1: On April 29, 2016, pursuant to the Agreement and Plan of Merger between MKS Instruments, Inc. ("MKS"), MKS' wholly-owned subsidiary, PSI Equipment, Inc. ("Merger Sub") and Newport Corporation ("Newport"), dated February 22, 2016 (the "Merger Agreement"), Merger Sub merged with and into Newport (the "Merger"), with Newport surviving the Merger as a wholly-owned subsidiary of MKS. This stock appreciation right, which has a base value of $20.32 and which became fully vested on March 31, 2013, was assumed by MKS in connection with the Merger and was converted from a stock appreciation right with respect to a total of 9,510 shares of Newport common stock having a base value of $12.47 per share.

F2: This stock appreciation right, which has a base value of $27.79 and which became fully vested on March 31, 2014, was assumed by MKS in connection with the Merger and was converted from a stock appreciation right with respect to a total of 6,840 shares of Newport common stock having a base value of $17.06 per share.

F3: This stock appreciation right, which has a base value of $27.89 and which became fully vested on March 31, 2015, was assumed by MKS in connection with the Merger and was converted from a stock appreciation right with respect to a total of 9,630 shares of Newport common stock having a base value of $17.12 per share.

F4: This stock appreciation right, which has a base value of $22.39 and which became fully vested on March 31, 2016, was assumed by MKS in connection with the Merger and was converted from a stock appreciation right with respect to a total of 16,800 shares of Newport common stock having a base value of $13.74 per share.

F5: These restricted stock units representing the right to receive a total of 2,952 shares of MKS' common stock, which vest on March 31, 2017, were assumed by MKS in connection with the Merger and were converted from restricted stock units representing the right to receive a total of 4,810 shares of Newport's common stock.

F6: This stock appreciation right, which has a base value of $29.80 and which vests in equal 1/3 installments on March 31, 2015, 2016 and 2017, was assumed by MKS in connection with the Merger and was converted from a stock appreciation right with respect to a total of 14,430 shares of Newport common stock having a base value of $18.29 per share.

F7: These restricted stock units representing the right to receive a total of 4,911 shares of MKS' common stock, which vest in two equal installments on March 31, 2017 and March 31, 2018, were assumed by MKS in connection with the Merger and were converted from restricted stock units representing the right to receive a total of 8,000 shares of Newport's common stock.

F8: This stock appreciation right, which has a base value of $31.13 and which vests in equal 1/3 installments on March 31, 2016, 2017 and 2018, was assumed by MKS in connection with the Merger and was converted from a stock appreciation right with respect to a total of 12,000 shares of Newport common stock having a base value of $19.11 per share.