Contract

RESTRICTED STOCK UNIT AWARD AGREEMENT This Restricted Stock Unit Award Agreement (this “Agreement”) is dated effective as of ________________, 202__, and is made by and between Eos Energy Enterprises, Inc., a Delaware corporation (f/k/a X. Xxxxx Principal Merger Corp. II) (the “Company”), and the Participant whose name appears on the signature page to this Agreement (“Executive”). Capitalized terms used herein and not defined shall have the meaning ascribed to such terms in the Eos Energy Enterprises, Inc. 2020 Incentive Plan, as amended from time to time. Witnesseth: Whereas, the Board has adopted the Plan to motivate Eligible Persons of the Company or its Affiliates by providing them with an ownership interest in the Company; Whereas, the Committee has approved the grant to Executive of the aggregate number of Restricted Stock Units set forth on the signature page to this Agreement; and Whereas, Executive and the Company desire to enter into an agreement to evidence and confirm the grant of such Restricted Stock Units on the terms and conditions set forth herein. Now, therefore, to evidence the Restricted Stock Units so granted, and to set forth the terms and conditions governing such Restricted Stock Units, the Company and Executive hereby agree as follows: 1. Grant. The Company hereby evidences and confirms its grant to Executive, effective as of the date hereof (the “Grant Date”), of the aggregate number of Restricted Stock Units set forth on the signature page hereof. 2. Vesting. (a) Vesting. Except as otherwise provided in this Agreement, subject to the continuous engagement or employment of Executive by the Company or any Affiliate through the applicable vesting date, the Restricted Stock Units shall vest [in three equal annual installments on each of the first three anniversaries of the Grant Date]; provided, that, the Restricted Stock Units shall vest in full (x) [upon the consummation of a Change in Control], or (y) subject to [Section XXX ] of that certain Employment Agreement, dated as of _________, 202__, by and between Executive and the Company (the “Employment Agreement”), upon the termination of Executive’s employment with the Company by the Company without Cause or by Executive for Good Reason (each as defined in the Employment Agreement)]. (b) Committee Acceleration. The Committee may accelerate the vesting of all or any portion of the Restricted Stock Units, at any time and from time to time. Notwithstanding the immediately preceding sentence, except as approved by the Committee and as set forth in the Employment Agreement, no Restricted Stock Units shall vest after the date on which Executive receives a notice of termination of engagement or employment from the Company or tenders a notice of termination to the Company, as applicable. 3. Other Termination. In the event Executive’s services to the Company and its Affiliates are terminated for any other reason, the Restricted Stock Units (or portion thereof) that are not vested as of Executive’s termination of services shall be immediately forfeited and cancelled on the date of such termination of services. 4. Transferability. Except as expressly permitted under Section 14(b) of the Plan, the Restricted Stock Units may not be sold, transferred, pledged, assigned or otherwise alienated or hypothecated, other than by will or by the laws of descent and distribution.

In Witness Whereof, the Company and Executive have executed this Restricted Stock Unit Award Agreement as of the date first above written. Eos Energy Enterprises, Inc. By: ________________________________ Name: Title: Executive _______________________________ [NAME] Number of Restricted Stock Units: [XXX,XXX]