Exhibit
4.2


 


SPECIMEN
CLASS A ORDINARY SHARE CERTIFICATE 


 


	NUMBER	 	SHARES


 


ONS
ACQUISITION CORP. 


INCORPORATED
UNDER THE LAWS OF THE CAYMAN ISLANDS 


CLASS
A ORDINARY SHARES 


 


SEE
REVERSE FOR 


CERTAIN
DEFINITIONS 


 


CUSIP
G67560105 


 


This
Certifies that                 is the owner of 


 


FULLY
PAID AND NON-ASSESSABLE CLASS A ORDINARY SHARES OF THE PAR VALUE OF 


US$0.0001
EACH OF ONS ACQUISITION CORP. (THE “COMPANY”) 


 


subject
to the Company’s amended and restated memorandum and articles of association, as the same may be amended from time to time, and
transferable on the books of the Company in person or by duly authorized attorney upon surrender of this certificate properly endorsed.



 


The
Company will be forced to redeem all of its Class A ordinary shares if it is unable to complete a business combination within the period
set forth in the Company’s amended and restated memorandum and articles of association, as the same may be amended from time to
time, all as more fully described in the Company’s final prospectus dated [__], 2021. 


 


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


 


Witness
the facsimile signatures of its duly authorized officers. 


 


	Dated:
    ______________________





	Chief
    Executive Officer	Cayman
    Islands	Chief
    Financial Officer
	 	 	 


 




     


     


    

 


ONS
ACQUISITION CORP.


 


The
Company will furnish without charge to each shareholder who so requests the powers, designations, preferences and relative, participating,
optional or other special rights of each class of shares or series thereof of the Company and the qualifications, limitations, or restrictions
of such preferences and/or rights. This certificate and the shares represented thereby are issued and shall be held subject to all the
provisions of the Company’s amended and restated memorandum and articles of association, as the same may be amended from time to
time, and resolutions of the Board of Directors providing for the issue of Class A ordinary shares (copies of which may be obtained from
the secretary of the Company), to all of which the holder of this certificate by acceptance hereof assents. 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	 	 
	 	 	 	 	 	 	 	 
	 	 	 	 	 	 	 	 	 	 	(Cust)	 	 	 	(Minor)
	 	 	 	 	 	 
	TEN
    ENT	 	—	 	as
    tenants by the entireties	 	 	 	 	 	under
    Uniform Gifts to Minors Act
	 	 	 	 	 	 
	 	 	 	 	 	 	 	 	 	 	(State)
	 	 	 	 	 	 	 	 
	JT
    TEN	 	—	 	as
    joint tenants with right of survivorship and not as tenants in common	 	 	 	 	 	 	 	 	 	 


 


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


 


For
value received, hereby sells, assigns and transfers unto


 




     


     


    

 


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


 


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


 


Shares
represented by the within Certificate, and does hereby irrevocably constitute and appoint Attorney to transfer the said shares on the
books of the within named Company with full power of substitution in the premises.


	 	 	 	 	 
	Dated:	 	 	 	 
	 	 	 	 	 
	 	 	 	 	Shareholder
	 	 	 	 
	 	 	 	 	NOTICE:
    THE SIGNATURE(S) 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:	 	 
	 	 	 	 
	By	 	 	 	 
	 	 	 
	 	 	 
	 	 	 


 


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 OR ANY SUCCESSOR RULE).


 


In
each case, as more fully described in the Company’s final prospectus dated [__], 2021, 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 its initial public
offering only in the event that (i) the Company redeems the Class A ordinary shares sold in its initial public offering and liquidates
because it does not consummate an initial business combination within the period of time set forth in the Company’s amended and
restated memorandum and articles of association, as the same may be amended from time to time, (ii) the Company redeems the Class A ordinary
shares sold in its initial public offering in connection with a shareholder vote to amend the Company’s amended and restated memorandum
and articles of association (A) that would modify the substance or timing of the Company’s obligation to provide holders of the
Class A ordinary shares the right to have their shares redeemed in connection with the Company’s initial business combination or
to redeem 100% of the Class A ordinary shares if the Company does not complete its initial business combination within the time period
set forth therein or (B) with respect to any other provision relating to the rights of holders of the Class A ordinary shares, or (iii)
if the holder(s) seek(s) to redeem for cash his, her or its respective Class A ordinary shares in connection with a tender offer (or
proxy solicitation, solely in the event the Company seeks shareholder 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.