X0508 4 2025-11-13 0 0001759631 Hyliion Holdings Corp. HYLN 0002011297 MOOK JOSHUA T. C/O HYLIION HOLDING CORP. 1202 BMC DRIVE, SUITE 100 CEDAR PARK TX 78613 0 1 0 0 Chief Technology Officer 0 Common Stock 2025-11-13 4 F 0 4110 1.68 D 524008 D Common Stock 2025-11-14 4 F 0 7397 1.70 D 516611 D Common Stock 2025-11-17 4 J 0 9039 1.66 D 507572 D Shares withheld for the payment of a tax liability related to the vesting and distribution of restricted stock units. 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. This transaction includes the sale of issuer common shares to cover the reporting person's tax withholding obligation for vesting dates on August 25, 2025. As a result of an administrative error by the issuer's third-party service provider, cash was paid on behalf of the reporting person for tax withholding obligations on the vesting date, August 25, 2025. A corresponding sale of issuer common shares to cover the reporting person's tax withholding obligation on August 25, 2025 could not be completed until the opening of the issuer's next window period. Accordingly, the the above shares attributed to the vesting on August 25, 2025 were sold November 17, 2025, the first available date during an open window period on which the shares could be sold on behalf of the reporting person. /s/ Joshua T. Mook 2025-11-17