Exhibit
4.3


 


	NUMBER

        ________-
	 	(SEE
                                         REVERSE SIDE FOR LEGEND)

        THIS
        WARRANT WILL BE VOID IF NOT EXERCISED PRIOR TO THE EXPIRATION DATE (DEFINED BELOW) 
	 	WARRANTS


 


PETRA
ACQUISITION, INC.


 


CUSIP
716421 110


 


WARRANT


 


THIS
CERTIFIES THAT, for value received


 


is
the registered holder of a warrant or warrants (the “Warrant(s)”) of Petra Acquisition, Inc., a Delaware corporation
(the “Company”), expiring at 5:00 p.m., New York City time, on the five year anniversary of the Company’s
completion of an initial merger, share exchange, asset acquisition, stock purchase, recapitalization, reorganization or other
similar business combination with one or more businesses or entities (a “Business Combination”), to purchase
one fully paid and non-assessable share of common stock, par value $0.001 per share (“Shares”), of the Company
for each whole Warrant evidenced by this Warrant Certificate. The Warrant entitles the holder thereof to purchase from the Company,
commencing on the later of (a) _______, 2020 and (b) 30 days after the Company’s completion of an initial Business Combination,
such number of Shares of the Company at the Warrant Price (as defined below), upon surrender of this Warrant Certificate and payment
of the Warrant Price at the office or agency of Continental Stock Transfer & Trust Company (the “Warrant Agent”),
but only subject to the conditions set forth herein and in the Warrant Agreement between the Company and Continental Stock Transfer
& Trust Company. In no event will the Company be required to net cash settle any warrant exercise. The Warrant Agreement provides
that upon the occurrence of certain events the Warrant Price, Redemption Trigger Price (defined below) and the number of Shares
purchasable hereunder, set forth on the face hereof, may, subject to certain conditions, be adjusted. The term “Warrant
Price” as used in this Warrant Certificate refers to the price per Share at which Shares may be purchased at the time
the Warrant is exercised. The initial Warrant Price per Share is equal to $11.50 per share.


 


No
fraction of a Share will be issued upon any exercise of a Warrant. If the holder of a Warrant would be entitled to receive a fraction
of a Share upon any exercise of a Warrant, the Company shall, upon such exercise, round up to the nearest whole number the number
of Shares to be issued to such holder.


 


Upon
any exercise of the Warrant for less than the total number of full Shares provided for herein, there shall be issued to the registered
holder hereof or the registered holder’s assignee a new Warrant Certificate covering the number of Shares for which the
Warrant has not been exercised.


 


Warrant
Certificates, when surrendered at the office or agency of the Warrant Agent by the registered holder in person or by attorney
duly authorized in writing, may be exchanged in the manner and subject to the limitations provided in the Warrant Agreement, but
without payment of any service charge, for another Warrant Certificate or Warrant Certificates of like tenor and evidencing in
the aggregate a like number of Warrants.


 


Upon
due presentment for registration of transfer of the Warrant Certificate at the office or agency of the Warrant Agent, a new Warrant
Certificate or Warrant Certificates of like tenor and evidencing in the aggregate a like number of Warrants shall be issued to
the transferee in exchange for this Warrant Certificate, subject to the limitations provided in the Warrant Agreement, without
charge except for any applicable tax or other governmental charge.


 


The
Company and the Warrant Agent may deem and treat the registered holder as the absolute owner of this Warrant Certificate (notwithstanding
any notation of ownership or other writing hereon made by anyone), for the purpose of any exercise hereof, of any distribution
to the registered holder, and for all other purposes, and neither the Company nor the Warrant Agent shall be affected by any notice
to the contrary.


 


This
Warrant does not entitle the registered holder to any of the rights of a stockholder of the Company.


 


The
Company reserves the right to call the Warrant at any time prior to its exercise with a notice of call in writing to the holders
of record of the Warrant, giving at least 30 days’ notice of such call, at any time while the Warrant is exercisable, if
the last sale price of the Shares has been at least $16.50 per share (“Redemption Trigger Price”) on each of
20 trading days within any 30 trading day period (the “30-day trading period”) ending on the third business
day prior to the date on which notice of such call is given and if, and only if, there is a current registration statement in
effect with respect to the Shares underlying the Warrants commencing five business days prior to the 30-day trading period and
continuing each day thereafter until the date of redemption. The call price of the Warrants is to be $0.01 per Warrant. Any Warrant
either not exercised or tendered back to the Company by the end of the date specified in the notice of call shall be canceled
on the books of the Company and have no further value except for the $0.01 call price.


 


By


 


	 	 	 
	President	 	Secretary


 




    


     


    

  


SUBSCRIPTION
FORM


To
Be Executed by the Registered Holder in Order to Exercise Warrants


 


The
undersigned Registered Holder irrevocably elects to exercise ______________ Warrants represented by this Warrant Certificate,
and to purchase the Common Stock issuable upon the exercise of such Warrants, and requests that Certificates for such shares shall
be issued in the name of


 


	(PLEASE
    TYPE OR PRINT NAME AND ADDRESS)
	 
	 


(SOCIAL
SECURITY OR TAX IDENTIFICATION NUMBER)


and
be delivered to _______________________________________________________________________


(PLEASE
PRINT OR TYPE NAME AND ADDRESS)


 


and,
if such number of Warrants shall not be all the Warrants evidenced by this Warrant Certificate, that a new Warrant Certificate
for the balance of such Warrants be registered in the name of, and delivered to, the Registered Holder at the address stated below:


 


	Dated:
    	 	 	 	 
	 	 	 	 	(SIGNATURE)
	 	 	 	 	 
	 	 	 	 	(ADDRESS)
	 	 	 	 	 
	 	 	 	 	 
	 	 	 	 	(TAX
    IDENTIFICATION NUMBER)





 


ASSIGNMENT


To
Be Executed by the Registered Holder in Order to Assign Warrants


 


For
Value Received, _______________________ hereby sell, assign, and transfer unto


 


	(PLEASE
    TYPE OR PRINT NAME AND ADDRESS)
	 
	 


(SOCIAL
SECURITY OR TAX IDENTIFICATION NUMBER)


and
be delivered to _______________________________________________________________________


(PLEASE
PRINT OR TYPE NAME AND ADDRESS)


 


______________________
of the Warrants represented by this Warrant Certificate, and hereby irrevocably constitute and appoint _________________________________
Attorney to transfer this Warrant Certificate on the books of the Company, with full power of substitution in the premises.


 


	Dated:
    	 	 	 	 
	 	 	 	 	(SIGNATURE)


 


The
signature to the assignment of the Subscription Form must correspond to the name written upon the face of this Warrant Certificate
in every particular, without alteration or enlargement or any change whatsoever, and must be guaranteed by a commercial bank or
trust company or a member firm of the NYSE American, Nasdaq, New York Stock Exchange, Pacific Stock Exchange, or Chicago
Stock Exchange.