Exhibit 4.3


 


[Form of Warrant Certificate]


 


[FACE]


 


Number


 


Warrants


 


THIS WARRANT SHALL BE VOID IF NOT EXERCISED
PRIOR TO


THE EXPIRATION OF THE EXERCISE PERIOD PROVIDED
FOR


IN THE WARRANT AGREEMENT DESCRIBED BELOW


 


MOUNT RAINIER ACQUISITION CORP.


Incorporated Under the Laws of the State of Delaware


  


CUSIP 623006 111


 


Warrant Certificate


 


This Warrant Certificate certifies that                    ,
or registered assigns, is the registered holder of warrant(s) evidenced hereby (the “Warrants” and each, a “Warrant”)
to purchase shares of common stock, $0.0001 par value per share (“Common Stock”), of Mount
Rainier Acquisition Corp., a Delaware corporation (the “Company”). Each whole Warrant entitles the holder, upon
exercise during the period set forth in the Warrant Agreement referred to below, to receive from the Company that number of fully paid
and non-assessable shares of Common Stock as set forth below, at the exercise price (the “Exercise Price”)
as determined pursuant to the Warrant Agreement, payable in lawful money (or through “cashless exercise”
as provided for in the Warrant Agreement) of the United States of America upon surrender of this Warrant Certificate and payment of the
Exercise Price at the office or agency of the Warrant Agent referred to below, subject to the conditions set forth herein and in the Warrant
Agreement. Defined terms used in this Warrant Certificate but not defined herein shall have the meanings given to them in the Warrant
Agreement.


 


Each whole Warrant is initially
exercisable for three-fourths fully paid and non-assessable share of Common Stock. No fractional shares will be issued upon exercise of
any Warrant. If, upon the exercise of Warrants, a holder would be entitled to receive a fractional interest in a share of Common Stock,
the Company will, upon exercise, round down to the nearest whole number the number of shares of Common Stock to be issued to the Warrant
holder. The number of shares of Common Stock issuable upon exercise of the Warrants is subject to adjustment upon the occurrence of certain
events set forth in the Warrant Agreement.


 


The initial Exercise Price
per share of Common Stock for any Warrant is equal to $11.50 per whole share. The Exercise Price is subject to adjustment upon the
occurrence of certain events set forth in the Warrant Agreement.


 


Subject to the conditions
set forth in the Warrant Agreement, the Warrants may be exercised only during the Exercise Period and to the extent not exercised by the
end of such Exercise Period, such Warrants shall become void.


 






     


     


    

 


Reference is hereby made
to the further provisions of this Warrant Certificate set forth on the reverse hereof and such further provisions shall for all purposes
have the same effect as though fully set forth at this place.


 


This Warrant Certificate
shall not be valid unless countersigned by the Warrant Agent, as such term is used in the Warrant Agreement.


 


This Warrant Certificate
shall be governed by and construed in accordance with the internal laws of the State of New York, without regard to conflicts of laws
principles thereof.


 


	 	Mount Rainier Acquisition Corp.
	 	 	 
	 	By:	         
	 	Name:	 
	 	Title:  	 
	 	 	 
	 	American Stock Transfer & Trust Company, LLC, as Warrant Agent
	 	 	 
	 	By:	 
	 	Name:	 
	 	Title:  	 


 






     


     


    

 


[Form of Warrant Certificate]


 


[Reverse]


 


The Warrants evidenced by
this Warrant Certificate are part of a duly authorized issue of Warrants entitling the holder on exercise to receive shares of Common
Stock and are issued or to be issued pursuant to a Warrant Agreement dated as of [__], 2021 (the “Warrant Agreement”),
duly executed and delivered by the Company to American Stock Transfer & Trust Company, LLC, a New York limited liability trust company,
as warrant agent (the “Warrant Agent”), which Warrant Agreement is hereby incorporated by
reference in and made a part of this instrument and is hereby referred to for a description of the rights, limitation of rights, obligations,
duties and immunities thereunder of the Warrant Agent, the Company and the holders (the words “holders” or “holder”
meaning the Registered Holders or Registered Holder, respectively) of the Warrants. A copy of the Warrant Agreement may be obtained by
the holder hereof upon written request to the Company. Defined terms used in this Warrant Certificate but not defined herein shall have
the meanings given to them in the Warrant Agreement.


 


Warrants may be exercised
at any time during the Exercise Period set forth in the Warrant Agreement. The holder of Warrants evidenced by this Warrant Certificate
may exercise them by surrendering this Warrant Certificate, with the form of election to purchase set forth hereon properly completed
and executed, together with payment of the Exercise Price as specified in the Warrant Agreement (or through “cashless exercise”
as provided for in the Warrant Agreement) at the principal corporate trust office of the Warrant Agent. In the event that upon any
exercise of Warrants evidenced hereby the number of Warrants exercised shall be less than the total number of Warrants evidenced hereby,
there shall be issued to the holder hereof or his, her or its assignee, a new Warrant Certificate evidencing the number of Warrants not
exercised.


 


Notwithstanding anything
else in this Warrant Certificate or the Warrant Agreement, no Warrant may be exercised unless at the time of exercise (i) a registration
statement covering the shares of Common Stock to be issued upon exercise is effective under the Securities Act and (ii) a prospectus
thereunder relating to the shares of Common Stock is current, except through “cashless exercise” as provided for in the Warrant
Agreement.


 


The Warrant Agreement provides
that upon the occurrence of certain events the number of shares of Common Stock issuable upon exercise of the Warrants set forth on the
face hereof may, subject to certain conditions, be adjusted. If, upon exercise of a Warrant, the holder thereof would be entitled
to receive a fractional interest in a share of Common Stock, the Company shall, upon exercise, round down to the nearest whole number
of shares of Common Stock to be issued to the holder of the Warrant.


 


Warrant Certificates, when
surrendered at the principal corporate trust office of the Warrant Agent by the Registered Holder thereof in person or by legal representative
or 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 evidencing in the aggregate
a like number of Warrants.


 


Upon due presentation for
registration of transfer of this Warrant Certificate at the office 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(s) in exchange for this
Warrant Certificate, subject to the limitations provided in the Warrant Agreement, without charge except for any tax or other governmental
charge imposed in connection therewith.


 






     


     


    

 


The Company and the
Warrant Agent may deem and treat the Registered Holder(s) hereof as the absolute owner(s) 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 holder(s) hereof, and for all other purposes, and neither the Company nor the Warrant Agent shall be
affected by any notice to the contrary. Neither the Warrants nor this Warrant Certificate entitles any holder hereof to any rights
of a stockholder of the Company.


 






     


     


    

 


Election to Purchase


 


(To Be Executed Upon Exercise of Warrant)


 


The undersigned hereby irrevocably
elects to exercise the right, represented by this Warrant Certificate, to receive                 
shares of Common Stock and herewith tenders payment for such shares of Common Stock to the order of Mount Rainier Acquisition Corp. (the “Company”)
in the amount of $         in accordance with the terms hereof. The undersigned requests
that a certificate for such shares of Common Stock be registered in the name of                 ,
whose address is                  and that such shares
of Common Stock be delivered to                                  
whose address is                 . If said number
of shares of Common Stock is less than all of the shares of Common Stock purchasable hereunder, the undersigned requests that a new Warrant
Certificate representing the remaining balance of such shares of Common Stock be registered in the name of                 ,
whose address is                         
and that such Warrant Certificate be delivered to                 ,
whose address is                 .


 


In the event that the Warrant
has been called for redemption by the Company pursuant to Section 6 of the Warrant Agreement and the Company has required cashless
exercise pursuant to Section 6.3 of the Warrant Agreement, the number of shares of Common Stock that this Warrant is exercisable
for shall be determined in accordance with subsection 3.3.1(b) and Section 6.3 of the Warrant Agreement.


 


In the event that the registration
statement required by Section 7.4 of the Warrant Agreement is not effective and current within ninety (90) days after the closing of the
initial business combination, the number of shares of Common Stock that this Warrant is exercisable for shall be determined in accordance
with subsection 3.3.1(d) of the Warrant Agreement.


 


In the event that the Warrant
may be exercised, to the extent allowed by the Warrant Agreement, through cashless exercise (i) the number of shares of Common Stock
that this Warrant is exercisable for would be determined in accordance with the relevant section of the Warrant Agreement which allows
for such cashless exercise and (ii) the holder hereof shall complete the following: The undersigned hereby irrevocably elects to
exercise the right, represented by this Warrant Certificate, through the cashless exercise provisions of the Warrant Agreement, to receive
shares of Common Stock. If said number of shares of Common Stock is less than all of the shares of Common Stock purchasable hereunder
(after giving effect to the cashless exercise), the undersigned requests that a new Warrant Certificate representing the remaining balance
of such shares of Common Stock be registered in the name of                 ,
whose address is                         
and that such Warrant Certificate be delivered to                 ,
whose address is                 .


 


[Signature Page Follows]


 


	Date:                , 21    	 	 
	 	 	(Signature)
	 	 	 



 


	 	 	 
	 	 	 
	 	 	 
	 	 	(Address)
	 	 	 
	 	 	 
	 	 	(Tax Identification Number)
	Signature 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 (OR ANY SUCCESSOR RULE)).