STOCK TITAN

ACM Research (NASDAQ: ACMR) director exercises 5,000 options, sells 5,000 shares

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

ACM Research, Inc. director Haiping Dun reported a mix of option exercises and share sales in Class A Common Stock. On May 19, 2026, he exercised stock options for 5,000 shares at an exercise price of $5.60 per share, then sold 5,000 shares in multiple open-market transactions at prices between $63.84 and $67.54. The filing notes these sales were made under a pre-arranged Rule 10b5-1 trading plan adopted on August 13, 2025. After these transactions, he reported no directly held Class A Common Stock, while indirect holdings include 755,090 shares held by the Haiping Dun & Chi-Pin H Dun Revocable Trust and 100,000 shares held by the Dun Family GST Trust.

Positive

  • None.

Negative

  • None.
Insider Dun Haiping
Role null
Sold 5,000 shs ($331K)
Type Security Shares Price Value
Exercise Stock Option 5,000 $0.00 --
Exercise Class A Common Stock 5,000 $5.60 $28K
Sale Class A Common Stock 1,333 $63.84 $85K
Sale Class A Common Stock 500 $65.09 $33K
Sale Class A Common Stock 1,309 $67.21 $88K
Sale Class A Common Stock 1,858 $67.54 $125K
holding Class A Common Stock -- -- --
holding Class A Common Stock -- -- --
Holdings After Transaction: Stock Option — 50,000 shares (Direct, null); Class A Common Stock — 5,000 shares (Direct, null); Class A Common Stock — 100,000 shares (Indirect, Dun Family GST Trust)
Footnotes (1)
  1. 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 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 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 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. The option is fully vested and exercisable.
Shares sold 5,000 shares Class A Common Stock sold in open market on May 19, 2026
Sale prices $63.84–$67.54 per share Range of weighted average sale prices on May 19, 2026
Options exercised 5,000 shares Stock option exercise into Class A Common Stock on May 19, 2026
Exercise price $5.60 per share Exercise price of stock option converted into 5,000 shares
Revocable trust holdings 755,090 shares Indirect Class A holdings via Haiping Dun & Chi-Pin H Dun Revocable Trust
GST trust holdings 100,000 shares Indirect Class A holdings via Dun Family GST Trust
Remaining options 50,000 options Stock options outstanding after 5,000-share exercise, expiring April 22, 2029
Net share direction net-sell 5,000 shares Transaction summary net of option exercise and sales
Rule 10b5-1 trading plan regulatory
"The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan"
A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.
weighted average price financial
"The price reported in Column 4 is a weighted average price."
Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.
Stock Option financial
"security_title: "Stock Option" with an expiration date of 2029-04-22"
A stock option is a contract that gives you the right to buy or sell a company's stock at a specific price within a certain time frame. People use them to potentially make money if the stock's price moves favorably or to protect against losses. It's like holding a coupon that can be used to buy or sell stock at a set price later on.
Class A Common Stock financial
"security_title: "Class A Common Stock" for the reported sales and exercises"
Class A common stock is a category of a company’s shares that carries a specific set of ownership rights—most commonly defined voting power and claims on dividends—set out in the company’s charter. For investors it matters because the class determines how much influence you have over corporate decisions, the share’s likely dividend and trading behavior, and how it compares in value to other share classes, like choosing a particular seat with different privileges at the company’s decision-making table.
fully vested and exercisable financial
"The option is fully vested and exercisable."
SEC Form 4
FORM 4UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB APPROVAL
OMB Number:3235-0287
Estimated average burden
hours per response:0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
X
Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
1. Name and Address of Reporting Person*
Dun Haiping

(Last)(First)(Middle)
C/O ACM RESEARCH, INC.
42307 OSGOOD ROAD, SUITE I

(Street)
FREMONT CALIFORNIA 94539

(City)(State)(Zip)

UNITED STATES

(Country)
2. Issuer Name and Ticker or Trading Symbol
ACM Research, Inc. [ ACMR ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
XDirector10% Owner
Officer (give title below)Other (specify below)
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
05/19/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm filed by One Reporting Person
Form filed by More than One Reporting Person
4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year)2A. Deemed Execution Date, if any (Month/Day/Year)3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeVAmount(A) or (D)Price
Class A Common Stock05/19/2026M5,000A$5.65,000D
Class A Common Stock05/19/2026S(1)1,333D$63.84(2)3,667D
Class A Common Stock05/19/2026S(1)500D$65.09(3)3,167D
Class A Common Stock05/19/2026S(1)1,309D$67.21(4)1,858D
Class A Common Stock05/19/2026S(1)1,858D$67.54(5)0D
Class A Common Stock100,000IDun Family GST Trust
Class A Common Stock755,090IHaiping Dun & Chi-Pin H Dun Revocable Trust
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year)3A. Deemed Execution Date, if any (Month/Day/Year)4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year)7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Stock Option$5.605/19/2026M5,000 (6)04/22/2029Class A Common Stock5,000$050,000D
Explanation of Responses:
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. The option is fully vested and exercisable.
/s/ Mark McKechnie, Attorney-in-Fact for Haiping Dun05/21/2026
** Signature of Reporting PersonDate
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transactions did ACMR director Haiping Dun report on May 19, 2026?

ACMR director Haiping Dun exercised options for 5,000 Class A shares at $5.60 and sold 5,000 shares in open-market trades. The sales occurred at prices between $63.84 and $67.54, according to the Form 4 disclosure.

Were Haiping Dun’s ACMR share sales made under a Rule 10b5-1 plan?

Yes. The Form 4 states the ACMR share sales were executed under a Rule 10b5-1 trading plan adopted on August 13, 2025. Such pre-arranged plans automate trades and can reduce the significance of trade timing as a signal.

What price did Haiping Dun receive for his ACMR Class A Common Stock sales?

Dun’s ACMR Class A Common Stock sales occurred at weighted average prices reflecting trades between $63.84 and $67.54 per share. The filing notes multiple transactions within these ranges and offers to provide detailed price breakdowns upon request.

How many ACMR shares did Haiping Dun acquire through option exercise?

He exercised stock options covering 5,000 ACMR Class A shares at an exercise price of $5.60 per share. A related derivative entry shows 5,000 options converted into 5,000 underlying shares, with 50,000 stock options remaining outstanding after the transaction.

What are Haiping Dun’s ACMR holdings after these transactions?

Following the reported trades, Dun listed no directly held ACMR Class A Common Stock. Indirectly, 755,090 shares are held by the Haiping Dun & Chi-Pin H Dun Revocable Trust and 100,000 shares by the Dun Family GST Trust, as disclosed in the Form 4.

How does the Form 4 characterize the ACMR option involved in the exercise?

The Form 4 describes the ACMR stock option as fully vested and exercisable, with a conversion or exercise price of $5.60 per share and an expiration date of April 22, 2029. On May 19, 2026, 5,000 option shares were exercised into Class A Common Stock.