Mercury Systems director Plunkett gets 2,348 stock units

The DSUs vest by reference to the first anniversary or next annual meeting, but convert into common stock only when Plunkett ceases to be a board member.

Rhea-AI Filing Summary

Mercury Systems director Debora A. Plunkett acquired 2,348 deferred stock units (DSUs) on October 28, 2026. The DSUs vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders; vested DSUs convert into common stock only when she ceases to be a board member. Her reported post-transaction position was 19,181 shares.

Insider Trade Summary

Grant/Award: 2,348 shares

Grant/Award 1 txn

Insider Plunkett Debora A

Role Director

Type	Security	Shares	Price	Value
Grant/Award	Common Stock F1	2,348	$0.00	$0.00

Holdings After Transaction: Common Stock — 19,181 shares (Direct)

Footnotes (1)

1. F1. Represents deferred stock units (DSUs) that vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs do not convert into shares of common stock until the date on which the reporting person ceases to be a member of our Board of Directors.

Key Figures

Deferred stock units acquired: 2,348 DSUs Reported post-transaction position: 19,181 shares

2 metrics

Deferred stock units acquired 2,348 DSUs October 28, 2026

Reported post-transaction position 19,181 shares Following the DSU acquisition

Key Terms

deferred stock units, vested DSUs

2 terms

deferred stock units financial

"Represents deferred stock units (DSUs)"

Deferred stock units are promises from a company to give an employee shares of stock at a future date, often after certain conditions are met or after leaving the company. They function like a form of delayed compensation, allowing employees to earn shares over time. For investors, they represent potential future ownership in the company, but do not provide immediate voting rights or dividends until the shares are actually received.

vested DSUs financial

"Vested DSUs do not convert into shares"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many DSUs did MRCY director Debora A. Plunkett receive?

Debora A. Plunkett acquired 2,348 DSUs on October 28, 2026. Her reported post-transaction position was 19,181 shares.

When do Debora A. Plunkett’s Mercury Systems DSUs vest and convert?

The DSUs vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs convert into common stock only when Plunkett ceases to be a member of the board.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

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Available on EDGAR 10/29/2026 - 05:10 PM EDT Accepted by SEC EDGAR 10/29/2026 - 05:10 PM EDT Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Plunkett Debora A

(Last) (First) (Middle)

50 MINUTEMAN ROAD

(Street)

ANDOVER MASSACHUSETTS 01810

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
MERCURY SYSTEMS INC [ MRCY ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/28/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	10/28/2026		A		2,348(1)	A	$0	19,181	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents deferred stock units (DSUs) that vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs do not convert into shares of common stock until the date on which the reporting person ceases to be a member of our Board of Directors.

	/s/ Douglas Munro, attorney-in-fact	10/29/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)