<SEC-DOCUMENT>0001104659-21-020590-index.html : 20210211
<SEC-HEADER>0001104659-21-020590.hdr.sgml : 20210211
<ACCEPTANCE-DATETIME>20210211150228
ACCESSION NUMBER:		0001104659-21-020590
CONFORMED SUBMISSION TYPE:	SC 13G/A
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20210211
DATE AS OF CHANGE:		20210211

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TREX CO INC
		CENTRAL INDEX KEY:			0001069878
		STANDARD INDUSTRIAL CLASSIFICATION:	LUMBER & WOOD PRODUCTS (NO FURNITURE) [2400]
		IRS NUMBER:				541910453
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-56187
		FILM NUMBER:		21618982

	BUSINESS ADDRESS:	
		STREET 1:		160 EXETER DRIVE
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22603-8605
		BUSINESS PHONE:		5405426300

	MAIL ADDRESS:	
		STREET 1:		160 EXETER DRIVE
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22603-8605

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC
		CENTRAL INDEX KEY:			0001644956
		IRS NUMBER:				472614791
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G/A

	BUSINESS ADDRESS:	
		STREET 1:		150 NORTH RIVERSIDE PLAZA
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606
		BUSINESS PHONE:		312-236-1600

	MAIL ADDRESS:	
		STREET 1:		150 NORTH RIVERSIDE PLAZA
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606
</SEC-HEADER>
<DOCUMENT>
<TYPE>SC 13G/A
<SEQUENCE>1
<FILENAME>tm216055-9_sc13ga.htm
<DESCRIPTION>SC 13G/A
<TEXT>
Document 1 - file: tm216055-9_sc13ga.htm

</DOCUMENT>
</SEC-DOCUMENT>