X0306 4 2021-09-30 0 0001805077 Eos Energy Enterprises, Inc. EOSE 0001464790 B. Riley Financial, Inc. 11100 SANTA MONICA BLVD SUITE 800 LOS ANGELES CA 90025 0 0 1 0 0001880803 BRF Investments, LLC 11100 SANTA MONICA BLVD SUITE 800 LOS ANGELES CA 90025 0 0 1 0 0001207269 RILEY BRYANT R 11100 SANTA MONICA BLVD., SUITE 800 LOS ANGELES CA 90025 0 0 1 0 Class A Common Stock 5765942 I By BRF Investments, LLC Class A Common Stock 1769 D Warrants (right to buy) 11.5 2021-05-22 2025-11-16 Class A Common Stock 325000 325000 I By BRF Investments, LLC This Form 4 is being filed jointly by B. Riley Financial, Inc. ("BRF"), BRF Investments, LLC ("BRFI"), and Bryant R. Riley. BRF is the parent company of BRFI. As a result, BRF may be deemed to indirectly beneficially own the shares held by BRFI. 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. Each of BRF, BRFI, 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. Represents shares held directly by Bryant R. Riley. As of September 30, 2021, by virtue of the removal of any trading and voting power authority in any capacity of BRF, B. Riley Capital Management, LLC, a New York limited liability company, a registered investment advisor ("BRCM"), and Bryant R. Riley over the assets of BRC Partners Opportunity Fund, LP, a Delaware limited partnership ("BRPLP"), BRF, BRCM and Bryant R. Riley no longer may be deemed to beneficially own the shares/warrants held by BRPLP. B. Riley Financial, Inc., by: /s/ Bryant R. Riley, Co-Chief Executive Officer 2021-10-29 BRF Investments, LLC., by: /s/ Phillip Ahn, Authorized Signatory 2021-10-29 /s/ Bryant R. Riley 2021-10-29