Hyliion CTO Mook reports performance share conversions

Q: How many HYLN performance stock incentive units did Joshua T. Mook report?

Mook reported conversion-related transactions involving 55,981 and 71,341 performance stock incentive units on September 30, 2026. The respective award footnotes state that 25% and 20% vested after meeting the stated stock-price condition.

The two award groups have different issuance schedules, with the 71,341-unit group scheduled for December 31, 2028.

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Rhea-AI Filing Summary

Hyliion Holdings Corp. Chief Technology Officer Joshua T. Mook reported conversion-related transactions involving 55,981 and 71,341 performance stock incentive units on September 30, 2026. The respective award footnotes state that 25% and 20% vested upon meeting a minimum $4.00-per-share closing-price threshold over a 180-calendar-day average; the underlying conditions were satisfied September 28 and approved September 30. Half of the vested 55,981-unit award is scheduled for issuance September 30, 2027, with the remainder December 31, 2027; the 71,341-unit award is scheduled for issuance December 31, 2028.

Insider Trade Summary

127,322 shares exercised/converted

Exercise 4 txns

Insider MOOK JOSHUA T.

Role Chief Technology Officer

Type	Security	Shares	Price	Value
Conversion	Performance Stock Incentive Units ^F3	55,981	$0.00	$0.00
Conversion	Performance Stock Incentive Units ^F4	71,341	$0.00	$0.00
Conversion	Common Stock ^F1	55,981	$0.00	$0.00
Conversion	Common Stock ^F2	71,341	$0.00	$0.00

Holdings After Transaction: Performance Stock Incentive Units — 437,949 contracts (Direct); Common Stock — 1,223,928 shares (Direct)

Footnotes (4)

F1. The underlying market conditions for vesting of this portion of performance stock incentive units ("PSU Award") were satisfied on September 28, 2026, and subsequently approved by the Compensation Committee on September 30, 2026. Half of the vested PSUs will be issued on September 30, 2027 with the remainder to be issued on December 31, 2027.
F2. The underlying market conditions for vesting of this portion of performance stock incentive units ("PSU Award") were satisfied on September 28, 2026, and subsequently approved by the Compensation Committee on September 30, 2026. These vested PSUs will be issued on December 31, 2028.
F3. 25% of these PSU Awards vested upon the achievement of the underlying closing stock price threshold of a minimum of $4.00 per share over a 180-calendar-day average.
F4. 20% of these PSU Awards vested upon the achievement of the underlying closing stock price threshold of a minimum of $4.00 per share over a 180-calendar-day average.

Key Figures

Performance stock incentive units: 55,981 units Performance stock incentive units: 71,341 units Closing stock price threshold: Minimum $4.00 per share +3 more

6 metrics

Performance stock incentive units 55,981 units Conversion-related transaction reported September 30, 2026

Performance stock incentive units 71,341 units Conversion-related transaction reported September 30, 2026

Closing stock price threshold Minimum $4.00 per share Vesting condition for the reported awards

Average period 180 calendar days Period used for the closing stock price condition

Vested portion 25% Performance stock incentive unit award

Vested portion 20% Performance stock incentive unit award

Key Terms

performance stock incentive units, PSU Award, closing stock price threshold, 180-calendar-day average

4 terms

performance stock incentive units financial

"vesting of this portion of performance stock incentive units"

PSU Award financial

"performance stock incentive units ("PSU Award")"

closing stock price threshold financial

"underlying closing stock price threshold"

180-calendar-day average financial

"over a 180-calendar-day average"

FAQ

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

How many HYLN performance stock incentive units did Joshua T. Mook report?

Mook reported conversion-related transactions involving 55,981 and 71,341 performance stock incentive units on September 30, 2026. The respective award footnotes state that 25% and 20% vested after meeting the stated stock-price condition.

When will Joshua T. Mook's HYLN vested awards be issued?

Half of the vested 55,981-unit award is scheduled for issuance September 30, 2027, and the remainder December 31, 2027. The 71,341-unit award is scheduled for issuance December 31, 2028.

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

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Available on EDGAR 10/01/2026 - 05:59 PM Accepted by SEC EDGAR 10/01/2026 - 05:59 PM

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^*

MOOK JOSHUA T.

(Last)

(First)

(Middle)

C/O HYLIION HOLDING CORP.

1202 BMC DRIVE, SUITE 100

(Street)

CEDAR PARK

TEXAS

78613

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Hyliion Holdings Corp. [ HYLN ]

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

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

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	09/30/2026		C⁽¹⁾		55,981	A	$0	1,152,587	D
Common Stock	09/30/2026		C⁽²⁾		71,341	A	$0	1,223,928	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Performance Stock Incentive Units	⁽³⁾	09/30/2026		C			55,981	02/19/2026	12/31/2027	Common Stock	55,981	$0	223,924	D
Performance Stock Incentive Units	⁽⁴⁾	09/30/2026		C			71,341	12/31/2028	12/31/2028	Common Stock	71,341	$0	214,025	D

Explanation of Responses:

1. The underlying market conditions for vesting of this portion of performance stock incentive units ("PSU Award") were satisfied on September 28, 2026, and subsequently approved by the Compensation Committee on September 30, 2026. Half of the vested PSUs will be issued on September 30, 2027 with the remainder to be issued on December 31, 2027.

2. The underlying market conditions for vesting of this portion of performance stock incentive units ("PSU Award") were satisfied on September 28, 2026, and subsequently approved by the Compensation Committee on September 30, 2026. These vested PSUs will be issued on December 31, 2028.

3. 25% of these PSU Awards vested upon the achievement of the underlying closing stock price threshold of a minimum of $4.00 per share over a 180-calendar-day average.

4. 20% of these PSU Awards vested upon the achievement of the underlying closing stock price threshold of a minimum of $4.00 per share over a 180-calendar-day average.

Remarks:

	/s/ Joshua T. Mook	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)

Source: View Original Filing on SEC EDGAR