X0306 4 2021-02-17 0001499422 RBB Bancorp RBB 0001711531 Lin Ko-Yen 1055 WILSHIRE BLVD SUITE 1200 LOS ANGELES CA 90017 1 Common Stock, No Par Value 2021-02-17 4 M 0 10763 11.1498 A 116591 D Common Stock, No Par Value 2021-02-18 4 S 0 10763 18.6775 D 105828 D Option (right to buy) 11.1498 2021-02-17 4 M 0 10763 11.1498 D 2012-05-16 Common Stock 10763 0 D Option (right to buy) 11.1498 2023-05-15 Common Stock 10763 10763 D Option (right to buy) 18.2500 2026-05-17 Common Stock 10000 10000 D Exercise of reporting person's stock options that would otherwise expire 05/16/2022, of which shares were sold to pay the exercise price, to cover withholding taxes, and to pay broker fees and commissions, pursuant to a broker-assisted cashless exercise and sale. Price reflected is the weighted-average sale price for shares sold. The shares were sold in multiple transactions, and the range of sale prices for the transactions reported was $18.52 to $18.79. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or any staff member of the Securities and Exchange Commission, upon request, information regarding the number of shares sold at each separate price. These options vest in three equal annual installments beginning one year after the 05/16/2012 date of grant. These options vest in three equal annual installments beginning one year after the 05/15/2013 date of grant. These options vest in three equal annual installments beginning one year after the 05/17/2016 date of grant. Ko-Yen Lin is reporting a cashless exercise and sale of 10,763 shares /s/ Ko-Yen Lin 2021-02-19