X0306 4 2020-02-17 0 0001262823 WESTLAKE CHEMICAL CORP WLK 0001488587 Buesinger Robert F. 2801 POST OAK BOULEVARD, SUITE 600 HOUSTON TX 77056 0 1 0 0 EVP, Vinyl Products Common Stock 2020-02-17 4 M 0 3306 A 11487 D Common Stock 2020-02-18 4 F 0 918 60.523 D 10569 D Restricted Stock Units 2020-02-17 4 M 0 3306 0 D Common Stock 3306 00 D Restricted stock units convert into Issuer's shares of common stock on a one-for-one basis. On February 17, 2017, the reporting person was granted 3,306 restricted stock units vesting on the third anniversary of the grant date. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $60.50 to $60.873, inclusive. The reporting person undertakes to provide to Westlake Chemical Corp., any security holder of Westlake Chemical Corp. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. Robert F. Buesinger by J. Feng POA 2020-02-19