X0306 4 2019-09-05 0 0001394056 ONE STOP SYSTEMS, INC. OSS 0001283973 REARDON JOHN RALPH 2235 ENTERPRISE STREET #110 ESCONDIDO CA 92029 1 0 0 0 Common Stock 2019-09-05 4 S 0 10000 2.38 D 78863 I By: The RTC Group, Inc. Common Stock 2019-09-06 4 S 0 10000 2.46 D 68863 I By: The RTC Group, Inc. The price reported in column 4 is a weighted average price. These shares were sold in multiple transactions executed on the same day at prices ranging from $2.35 to $2.45 per share, inclusive. The reporting person undertakes to provide One Stop Systems, Inc., any security holder of One Stop Systems, Inc., or the staff of the Securities and Exchange Commission, upon request, the full information regarding the number of shares sold at each separate price within the range set forth in footnote (1) to this Form 4. Mr. Reardon has sole voting and investment control over The RTC Group, Inc. The price reported in column 4 is a weighted average price. These shares were sold in multiple transactions executed on the same day at prices ranging from $2.44 to $2.50 per share, inclusive. The reporting person undertakes to provide One Stop Systems, Inc., any security holder of One Stop Systems, Inc., or the staff of the Securities and Exchange Commission, upon request, the full information regarding the number of shares sold at each separate price within the range set forth in footnote (4) to this Form 4. /s/John R. Reardon 2019-09-17