Exhibit 4.1


 


	NUMBER 	UNITS
	U-	 


 


SEE REVERSE FOR CERTAIN DEFINITIONS


 


CUSIP 05586Y 205


 


B. RILEY PRINCIPAL MERGER CORP. 


 


UNITS CONSISTING OF ONE SHARE OF COMMON
STOCK AND ONE-HALF OF ONE REDEEMABLE WARRANT,

EACH WHOLE WARRANT ENTITLING THE HOLDER TO PURCHASE ONE SHARE OF COMMON STOCK


 


THIS CERTIFIES THAT                     
is the owner of          Units.


 


Each Unit (“Unit”)
consists of one (1) share of Class A common stock, par value $0.0001 per share (“Common Stock”),
of B. Riley Principal Merger Corp., a Delaware corporation (the “Company”), and one-half of one redeemable
warrant (the “Warrant”). Each whole Warrant entitles the holder to purchase one share of Common
Stock for $11.50 per share (subject to adjustment). Each Warrant will become exercisable on the later of (i) thirty (30) days
after the Company’s completion of a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or
other similar business combination with one or more businesses (each a “Business Combination”), or (ii) twelve
(12) months from the closing of the Company’s initial public offering, and will expire unless exercised before 5:00
p.m., New York City Time, on the date that is five (5) years after the date on which the Company completes its initial Business
Combination, or earlier upon redemption or liquidation (the “Expiration Date”). The Common Stock
and Warrants comprising the Units represented by this certificate are not transferable separately prior to                                               ,
2019, unless B. Riley FBR, Inc. elects to allow separate trading earlier, subject to the Company’s filing of a Current Report
on Form 8-K with the Securities and Exchange Commission containing an audited balance sheet reflecting the Company’s
receipt of the gross proceeds of the Company’s initial public offering and filing a Current Report on Form 8-K and issuing
a press release announcing when separate trading will begin. No fractional Warrants will be issued upon separation of the Units.
The terms of the Warrants are governed by a Warrant Agreement, dated as of, 2019, between the Company and Continental Stock Transfer &
Trust Company, as Warrant Agent, and are subject to the terms and provisions contained therein, all of which terms and provisions
the holder of this certificate consents to by acceptance hereof. Copies of the Warrant Agreement are on file at the office
of the Warrant Agent at 1 State Street, 30th Floor, New York, New York 10004, and are available to any Warrant holder
on written request and without cost.


 


This certificate is not valid unless countersigned
by the Transfer Agent and registered by the Registrar of the Company.


 


This certificate shall be governed by and
construed in accordance with the internal laws of the State of New York.


 


Witness the facsimile signature of a duly
authorized signatory of the Company.


 


	 	 	 
	Authorized Signatory	 	Transfer Agent


 




     


     


    

 


B. Riley Principal Merger Corp. 


 


The Company will furnish without charge
to each unitholder who so requests, a statement of the powers, designations, preferences and relative, participating, optional
or other special rights of each class of equity or series thereof of the Company and the qualifications, limitations, or restrictions
of such preferences and/or rights.


 


The following
abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out
in full according to applicable laws or regulations: 


 


	TEN COM	—	as tenants in common	UNIF GIFT MIN ACT	—	 	Custodian	 
	TEN ENT	—	as tenants by the entireties	 	 	(Cust)	 	(Minor)





	JT TEN	—	as joint tenants with right of survivorship and not as tenants in common	 	under Uniform Gifts to Minors Act
	 	 	 	 	 	 
	 	 	 	 	 	 
	 	 	 	(State)


 


Additional abbreviations may also be used
though not in the above list.


 


For value received,                     
hereby sell, assign and transfer unto                     



 


 


(PLEASE INSERT SOCIAL SECURITY OR OTHER
IDENTIFYING NUMBER OF ASSIGNEE)


 


 


(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING
ZIP CODE, OF ASSIGNEE)


 


Units represented by the within Certificate,
and do hereby irrevocably constitute and appoint 


 


Attorney to transfer the said Units on the books of
the within named Company with full power of substitution in the premises.


 


Dated 


 


	 	 	 
	 	 	 
	 	 	Notice: The signature to this assignment must correspond with the name as written upon the face of the certificate in every particular, without alteration or enlargement or any change whatever.


 


	Signature(s) Guaranteed:	 	 
	 	 	 
	 	 	 
	THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15 UNDER THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED (OR ANY SUCCESSOR RULE)).	 	 


 


As more fully described in, and subject to the terms and conditions
described in, the Company’s final prospectus for its initial public offering dated                   ,
2019, the holder(s) of this certificate shall be entitled to receive a pro rata portion of certain funds held in the trust
account established in connection with the Company’s initial public offering only in the event that (i) the Company
redeems the shares of Common Stock sold in the Company’s initial public offering and liquidates because it does not consummate
an initial business combination by the date set forth in the Company’s Second Amended and Restated Certificate of Incorporation,
as the same may be amended from time to time (the “Last Date”), (ii) the Company redeems the shares of Common
Stock sold in its initial public offering properly submitted in connection with a stockholder vote to amend the Company’s
Second Amended and Restated Certificate of Incorporation to modify the substance or timing of the Company’s obligation to
redeem 100% of the common stock if it does not consummate an initial business combination by the Last Date, or (iii) if the
holder(s) seek(s) to redeem for cash his, her or its respective shares of common stock in connection with a tender offer
(or proxy solicitation, solely in the event the Company seeks stockholder approval of the proposed initial business combination)
setting forth the details of a proposed initial business combination. In no other circumstances shall the holder(s) have any
right or interest of any kind in or to the trust account.