Sec Form 4 Filing - B. Riley Financial, Inc. @ Eos Energy Enterprises, Inc. - 2021-09-07

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person B. Riley Financial, Inc. 2. Issuer Name and Ticker or Trading Symbol Eos Energy Enterprises, Inc. [ EOSE] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 11100 SANTA MONICA BLVD SUITE 800 3. Date of Earliest Transaction (MM/DD/YY) 09/07/2021 (Street) LOS ANGELES, CA90025 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 Class A Common Stock 09/07/2021 S 38,544 D $ 13.7787 25,671 I By BRC Partners Opportunity Fund, LP ( 1 ) ( 2 ) Class A Common Stock 09/08/2021 S 300 D $ 13.6033 25,371 I By BRC Partners Opportunity Fund, LP ( 1 ) ( 2 ) Class A Common Stock 09/09/2021 S 25,371 D $ 13.4103 0 I By BRC Partners Opportunity Fund, LP ( 1 ) ( 2 ) Class A Common Stock 3,871,250 I By B. Riley Principal Sponsor Co. II, LLC ( 1 ) ( 2 ) Class A Common Stock 2,167,000 I By BRF Investments, LLC ( 1 ) ( 2 ) Class A Common Stock 20,000 D ( 3 ) Class A Common Stock 5,000 I By Bryant R. Riley, as UTMA custodian for Charlie Riley ( 1 ) ( 2 ) Class A Common Stock 5,000 I By Bryant R. Riley, as UTMA custodian for Susan Riley ( 1 ) ( 2 ) Class A Common Stock 5,000 I By Bryant R. Riley, as UTMA custodian for Abigail Riley ( 1 ) ( 2 ) Class A Common Stock 5,000 I By Bryant R. Riley, as UTMA custodian for Eloise Riley ( 1 ) ( 2 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 Warrants (right to buy) $ 11.5 05/22/2021 11/16/2025 Class A Common Stock 325,000 325,000 I By B. Riley Principal Sponsor Co. II, LLC ( 1 ) ( 2 ) Warrants (right to buy) $ 11.5 05/22/2021 11/16/2025 Class A Common Stock 25,000 25,000 I By BRC Partners Opportunity Fund, LP ( 1 ) ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other B. Riley Financial, Inc. 11100 SANTA MONICA BLVD SUITE 800 LOS ANGELES, CA90025 X BRF Investments, LLC 11100 SANTA MONICA BLVD SUITE 800 LOS ANGELES, CA90025 X B. Riley Principal Sponsor Co. II, LLC 299 PARK AVENUE 21ST FLOOR NEW YORK, NY10171 X B. RILEY PRINCIPAL INVESTMENTS, LLC 11100 SANTA MONICA BLVD SUITE 800 LOS ANGELES, CA90025 X B. RILEY CAPITAL MANAGEMENT, LLC 11100 SANTA MONICA BLVD. SUITE 800 LOS ANGELES, CA90025 X BRC Partners Management GP, LLC 11100 SANTA MONICA BLVD SUITE 800 LOS ANGELES, CA90025 X BRC Partners Opportunity Fund, LP 11100 SANTA MONICA BLVD. SUITE 800 LOS ANGELES, CA90025 X B. Riley Securities, Inc. 11100 SANTA MONICA BLVD SUITE 800 LOS ANGELES, CA90025 X RILEY BRYANT R 11100 SANTA MONICA BLVD., SUITE 800 LOS ANGELES, CA90025 X Signatures B. Riley Financial, Inc., by: /s/ Bryant R. Riley, Co-Chief Executive Officer 09/09/2021 Signature of Reporting Person Date BRF Investments, LLC., by: /s/ Phillip Ahn, Authorized Signatory 09/09/2021 Signature of Reporting Person Date B. Riley Principal Sponsor Co. II, LLC, by: /s/ Phillip Ahn, Authorized Signatory 09/09/2021 Signature of Reporting Person Date B. Riley Principal Investments, LLC, by: /s/ Kenneth Young, Chief Executive Officer 09/09/2021 Signature of Reporting Person Date B. Riley Capital Management, LLC, by: /s/ Bryant R. Riley, Chief Executive Officer 09/09/2021 Signature of Reporting Person Date BRC Partners Management GP, LLC, by B. Riley Capital Management, LLC, its sole member, by: /s/ Bryant R. Riley, Chief Executive Officer 09/09/2021 Signature of Reporting Person Date BRC Partners Opportunity Fund, L.P., by: /s/ Bryant R. Riley, Chief Investment Officer 09/09/2021 Signature of Reporting Person Date B. Riley Securities, Inc.., by: /s/ Andrew Moore, Chief Executive Officer 09/09/2021 Signature of Reporting Person Date /s/ Bryant R. Riley 09/09/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )This Form 4 is being filed jointly by B. Riley Financial, Inc. ("BRF"), BRF Investments, LLC ("BRFI"), B. Riley Principal Sponsor Co. II, LLC (the "Sponsor"), B. Riley Principal Investments, LLC ("BRPI"), BRC Partners Opportunity Fund, LP ("BRPLP"), BRC Partners Opportunity Fund GP, LLC ("BRPGP"), B. Riley Capital Management, LLC ("BRCM"), B. Riley Securities, Inc. ("BRS"), and Bryant R. Riley. BRF is the parent company of BRFI and BRS. As a result, BRF may be deemed to indirectly beneficially own the shares held by BRFI and BRS, respectively. BRPI is the sole member of the Sponsor. BRF is the parent company of BRPI. As a result, BRF and BRPI may be deemed to indirectly beneficially own the shares held by the Sponsor. BRPGP is the general partner of BRPLP. BRCM is the sole member of BRPGP. BRF is the parent company of BRCM. As a result, BRF, BRPGP, and BRCM, may be deemed to indirectly beneficially own the shares held by BRPLP. ( 2 )Bryant R. Riley is the Co-Chief Executive Officer and Chairman of the Board of Directors of BRF. As a result, Bryant R. Riley may be deemed to indirectly beneficially own the shares of Common Stock directly held by BRFI, BRS, BRPLP and the Sponsor. Each of BRF, BRFI, the Sponsor, BRPI, BRPLP, BRPGP, BRCM, BRS, and Bryant R. Riley disclaims beneficial ownership of the outstanding shares of Common Stock reported herein, except to the extent of its/his respective pecuniary interest therein. ( 3 )Represents shares held directly by Bryant R. Riley.

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).

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