ACMR · ACM Research, Inc.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 21, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $75.76 to $76.68, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, 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 footnote (2), (3), and (4) to this Form 4.

The option is fully vested and exercisable.

The option is fully vested and exercisable.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 21, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $76.81 to $77.79, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 21, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $77.84 to $78.4, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $80.95 to $81.91, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $79.89 to $80.77, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, 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 footnote (2), (3), and (4) to this Form 4.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $81.97 to $82.33, inclusive.

The option is fully vested and exercisable.

The price per restricted stock unit is based on the average closing market price of the Issuer's common stock for the 30 trading days preceding the grant day.

The restricted stock units should be vested immediately prior to the 2027 annual meeting of stockholders of the issuer, subject to continued service.

The price per restricted stock unit is based on the average closing market price of the Issuer's common stock for the 30 trading days preceding the grant day.

The restricted stock units should be vested immediately prior to the 2027 annual meeting of stockholders of the issuer, subject to continued service.

The price per restricted stock unit is based on the average closing market price of the Issuer's common stock for the 30 trading days preceding the grant day.

The restricted stock units should be vested immediately prior to the 2027 annual meeting of stockholders of the issuer, subject to continued service.

The option will vest and become exercisable immediately prior to the 2027 annual meeting of stockholders of the issuer, subject to continued service through the vesting date.

The option will vest and become exercisable immediately prior to the 2027 annual meeting of stockholders of the issuer, subject to continued service through the vesting date.

The option will vest and become exercisable immediately prior to the 2027 annual meeting of stockholders of the issuer, subject to continued service through the vesting date.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 5, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $81.22 to $82.07, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 5, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $83.85 to $84.5, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 5, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $82.38 to $82.89, inclusive.

The option is fully vested and exercisable.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 5, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $85.27 to $85.72, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 5, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $83.61 to $84.4, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, 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 footnote (2), (3), (4), (5), (6), (7), and (8) to this Form 4.

The option is fully vested and exercisable.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $86.73 to $87.66, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 5, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $85.7 to $86.19, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $84.62 to $85.6, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $87.77 to $88.01, inclusive.

The option is fully vested and exercisable.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 5, 2026.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $84.63 to $85.6, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $83.61 to $84.24, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $85.7 to $86.57, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $90.24 to $91.22, inclusive.

The option is fully vested and exercisable.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $87.22 to $88.04, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, 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 footnote (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), and (12) to this Form 4.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $88.24 to $89.22, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $93.02 to $93.39, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $89.24 to $90.22, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on November 29, 2024.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $92.01 to $92.8, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $63.7 to $64.22, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, 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 footnote (2), (3), (4), and (5) to this Form 4.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $66.41 to $67.37, inclusive.

The option is fully vested and exercisable.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $64.78 to $65.77, inclusive.

The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $67.43 to $68.00, inclusive.