Exhibit
4.1


 


	NUMBER

        U-__________

         
	 	 	 	UNITS


 


	SEE
    REVERSE FOR

 CERTAIN DEFINITIONS	PETRA
    ACQUISITION, INC.	 


 


CUSIP
716421 201


 


UNITS
CONSISTING OF ONE SHARE OF COMMON STOCK AND


ONE-HALF
OF ONE WARRANT


 


THIS
CERTIFIES THAT__________________________________________________________________


 


is
the owner of_________________________________________________________________Units.


 


Each
Unit (“Unit”) consists of one (1) share of common stock, par value $0.001 per share (“Common Stock”),
of Petra Acquisition, Inc., a Delaware corporation (the “Company”), and one-half of one warrant (“Warrant”).
Each whole Warrant entitles the holder to purchase one share of Common Stock for $11.50 per share (subject to adjustment). Only
whole Warrants are exercisable. Each whole Warrant will become exercisable on the later of (i) 30 days after the Company’s
completion of an initial merger, capital stock exchange, asset acquisition, or other similar business combination with one or
more businesses or entities (a “Business Combination”) and (ii) 12 months from the closing of the Company’s
initial public offering (“IPO”), and will expire unless exercised before 5:00 p.m., New York City Time, on
the fifth anniversary of the completion of an initial Business Combination, or earlier upon redemption or liquidation. The
Common Stock and Warrant(s) comprising the Unit(s) represented by this certificate are not transferable separately until ninety
days following the effective date of the registration statement on Form S-1 filed with the Securities and Exchange Commission
(“SEC”) in connection with the Company’s IPO, unless LifeSci Capital LLC informs the Company of its decision
to allow earlier separate trading, except that in no event will the Common Stock and Warrants be separately tradeable until the
Company has filed a Current Report on Form 8-K with the SEC containing an audited balance sheet reflecting the Company’s
receipt of the gross proceeds of its IPO and issued a press release announcing when such separate trading will begin. The terms
of the Warrants are governed by a Warrant Agreement, dated as of ____, 2020, 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 Registrar of the Company.


Witness
the facsimile seal of the Company and the facsimile signatures of its duly authorized officers.


 


By


  


	 	[Seal] 	 
	Chairman	Secretary


 






    


     


    

 


Petra
Acquisition, Inc.


 


The
Company will furnish without charge to each shareholder who so requests, a statement of the powers, designations, preferences,
and relative, participating, optional, or other special rights of each class of stock 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	under
    Uniform Gifts to Minors
	 	 	and
    not as tenants in common	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 will 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) SHOULD 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).	 


 


The
holder(s) of this certificate shall be entitled to receive a pro-rata portion of the funds from the trust account with respect
to the common stock underlying this certificate only in the event that (i) the Company is forced to liquidate because it does
not consummate an initial business combination within the period of time set forth in the Company’s Amended and Restated
Certificate of Incorporation, as the same may be amended from time to time (the “Charter”) or (ii) if the holder seeks
to convert his shares upon consummation of, or sell his shares in a tender offer in connection with, an initial business combination
or in connection with certain amendments to the Charter. In no other circumstances shall the holder(s) have any right or interest
of any kind in or to the trust account.