Sec Form 4 Filing - Stidolph Russell Monoki @ Eos Energy Enterprises, Inc. - 2021-06-15

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 Stidolph Russell Monoki 2. Issuer Name and Ticker or Trading Symbol Eos Energy Enterprises, Inc. [ EOSE] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O ALTENERGY LLC, 137 ROWAYTON AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 06/15/2021 (Street) ROWAYTON, CT06853 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 Common Stock 06/15/2021 M 5,198 ( 1 ) A $ 0 ( 2 ) 5,198 D Common Stock 4,469,292 I See footnote ( 3 )

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 Restricted Stock Units $ 0 06/15/2021 M 5,198 06/15/2021 ( 4 ) Common Stock 5,198 $ 0 0 D Restricted Stock Units ( 5 ) 06/17/2021 A 3,762 ( 6 ) ( 4 ) Common Stock 3,762 $ 0 3,762 D Stock Option (Right to Buy) $ 19.94 06/17/2021 A 9,617 ( 7 ) 06/17/2026 Common Stock 9,617 $ 0 9,617 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Stidolph Russell Monoki C/O ALTENERGY LLC 137 ROWAYTON AVENUE ROWAYTON, CT06853 X X Signatures /s/ Russell Stidolph 09/08/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Restricted stock units vested ( 2 )Convert without cost to shares of common stock on a one-for-one basis. ( 3 )The shares reported in this Form 4 are shares of common stock in which Mr. Stidoloph has a pecuniary interest in that are held directly by AltEnergy I, AltEnergy II, AltEnergy V, AltEnergy VI, Bridge, Transmission or Bridge II. Mr. Stidolph is the managing director of AltEnergy, the managing member of each of AltEnergy I, AltEnergy II, AltEnergy V, AltEnergy VI, Bridge, Transmission and Bridge II, and has voting and dispositive power with respect to the securities owned by AltEnergy I, AltEnergy II, AltEnergy V, AltEnergy VI, Bridge, Transmission and Bridge II. Each of the Filing Persons disclaims beneficial ownership of the outstanding shares of common stock of the issuer reported herein except to the extent of its pecuniary interest therein. ( 4 )Not applicable. ( 5 )Each restricted stock unit represents a contingent right to receive one share of common stock ( 6 )The reporting person received restricted stock units which vest on the earlier of (i) the first anniversary of the grant date, and (ii) immediately prior to the date of the next annual shareholders meeting of the Company following the grant date; provided, that, the restricted stock units shall vest in full upon the consummation of a change in control. ( 7 )The reporting person was granted an option to purchase common stock which vests on the earlier of (i) the first anniversary of the grant date, and (ii) immediately prior to the date of the next annual shareholders meeting of the Company following the grant date; provided, that, the option shall vest in full upon the consummation of a change in control.

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).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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