Joshua T. Mook - 12 Dec 2025 Form 4 Insider Report for Hyliion Holdings Corp. (HYLN)

Role: Chief Technology Officer
Signature: /s/ Joshua T. Mook
Issuer symbol: HYLN
Transactions as of: 12 Dec 2025
Net transactions value: -$25,121
Form type: 4
Filing time: 15 Dec 2025, 17:15:03 UTC
Previous filing: 01 Dec 2025
Next filing: 13 Feb 2026
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
MOOK JOSHUA T.	Chief Technology Officer	C/O HYLIION HOLDING CORP., 1202 BMC DRIVE, SUITE 100, CEDAR PARK	/s/ Joshua T. Mook	15 Dec 2025	0002011297

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	HYLN	Common Stock	Other	$25,121	-12,949	-1.2%	$1.94	1,033,803	12 Dec 2025	Direct	F1

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	These shares were sold at the direction of the issuer under the terms of the issuer's award agreement with the reporting person. Under the award agreement, the decision to sell shares to cover the reporting person's tax withholding obligations is at the sole discretion of the issuer.