Cabot’s William F. Masterson III acquires plan units

The senior vice president's Phantom Stock Units are to be settled upon retirement or other termination of service.

Rhea-AI Filing Summary

Cabot Corp Senior Vice President William F. Masterson III acquired 24.1542 Phantom Stock Units on September 30, 2026, as a compensation-related award. The reported price was $76.9100 per unit, and the units correspond to Common Stock on a 1-for-1 basis. His directly held balance after the transaction was 553.8957 Phantom Stock Units. The units were acquired under the Corporation’s supplemental 401(k) plan and are to be settled upon his retirement or other termination of service.

Insider Trade Summary

Grant/Award: 24.1542 shares

Grant/Award 1 txn

Insider Masterson William F III

Role Senior Vice President

Type	Security	Shares	Price	Value
Grant/Award	Phantom Stock Units F1, F2	24.1542	$76.91	$2K

Holdings After Transaction: Phantom Stock Units — 553.8957 contracts (Direct)

Footnotes (2)

1. F1. 1 for 1
2. F2. The reported phantom stock units were acquired under the Corporation's supplemental 401(k) plan and are to be settled upon the reporting person's retirement or other termination of service.

Key Figures

Phantom Stock Units acquired: 24.1542 Phantom Stock Units Reported price per unit: $76.9100 per Phantom Stock Unit Direct holdings after transaction: 553.8957 Phantom Stock Units +1 more

4 metrics

Phantom Stock Units acquired 24.1542 Phantom Stock Units Award acquired September 30, 2026

Reported price per unit $76.9100 per Phantom Stock Unit Reported transaction price

Direct holdings after transaction 553.8957 Phantom Stock Units Reported following the transaction

Underlying Common Stock 24.1542 shares Phantom Stock Units convert on a 1-for-1 basis

Key Terms

Phantom Stock Units, supplemental 401(k) plan, termination of service

3 terms

Phantom Stock Units financial

"acquired 24.1542 Phantom Stock Units"

Phantom stock units are company promises that pay a cash or stock-equivalent award tied to the firm’s share price or value growth, but they do not issue actual shares. Think of them as a bonus check that moves with the stock like a mirror rather than handing over an ownership slice. Investors care because these awards can affect a company’s future cash obligations, executive incentives and reported expenses without causing share dilution.

supplemental 401(k) plan financial

"acquired under the Corporation's supplemental 401(k) plan"

termination of service financial

"retirement or other termination of service"

FAQ

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

How many Phantom Stock Units did CBT Senior Vice President William F. Masterson III acquire?

William F. Masterson III acquired 24.1542 Phantom Stock Units on September 30, 2026. The reported price was $76.9100 per unit, and his directly held balance afterward was 553.8957 Phantom Stock Units.

When are CBT Phantom Stock Units settled?

The units acquired under the Corporation’s supplemental 401(k) plan are to be settled upon William F. Masterson III’s retirement or other termination of service.

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

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Available on EDGAR 10/01/2026 - 03:50 PM Accepted by SEC EDGAR 10/01/2026 - 03:49 PM 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^*

Masterson William F III

(Last) (First) (Middle)

C/O CABOT CORPORATION

TWO SEAPORT LANE, SUITE 1400

(Street)

BOSTON MASSACHUSETTS 02210

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
CABOT CORP [ CBT ]

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/30/2026

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

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
Phantom Stock Units	(1)	09/30/2026		A		24.1542		(2)	(2)	Common Stock	24.1542	$76.91	553.8957	D

Explanation of Responses:

1. 1 for 1

2. The reported phantom stock units were acquired under the Corporation's supplemental 401(k) plan and are to be settled upon the reporting person's retirement or other termination of service.

	By: Mazda Cintron, pursuant to a power of attorney from William F. Masterson, III	10/01/2026
	** 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)