EX-4.1



 Exhibit 4.1 
  






 
 COMMON STOCK COMMON STOCK Trinseo S.A. TSE-0001 FORMED UNDER THE LAWS OF LUXEMBOURG CUSIP L9340P 10 1 SEE
REVERSE FOR CERTAIN DEFINITIONS THIS CERTIFIES THAT COUNTERSIGNED AND REGISTERED: AMERICAN STOCK TRANSFER AND TRUST COMPANY LLC (Brooklyn, N.Y.) TRANSFER AGENT AND REGISTRAR BY Authorized Signature is the record holder of FULLY PAID AND
NON-ASSESSABLE SHARES OF COMMON STOCK, $0.01 PAR VALUE PER SHARE, OF Trinseo S.A. transferable on the books of the Company in person or by duly authorized attorney upon surrender of this Certificate properly endorsed. This Certificate is not valid
until countersigned by the Transfer Agent and registered by the Registrar. WITNESS the facsimile seal of the Company and the facsimile signatures of its duly authorized officers. DATED: LUXEMBOURG TRINSEO S.A. number CORPORATE SEAL DIRECTOR DIRECTOR
JUNE 3, 2010 shares 







 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	  		 	under Uniform Gifts to Minors
		 		 	of survivorship and not as	  		 	Act
                                         
          
		 		 	tenants in common	  		 	(State)
		 		 		  	UNIF TRF MIN ACT	 	-              Custodian (until age         )
		 		 		  		 	    (Cust)
		 		 		  		 	               under Uniform Transfers
		 		 		  		 	    (Minor)
		 		 		  		 	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 

 
  
  

 

                          
                                         
                                         
                                         
                                         
           Shares 
 of the common stock represented by the within Certificate, and do hereby
irrevocably constitute and appoint
                                        
                                        
                                         
                                         
                                         
                                         
             

                          
                                         
                                         
                                         
                                         
       Attorney 
 to transfer the said stock 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.