Haiping Dun - 19 May 2026 Form 4 Insider Report for ACM Research, Inc. (ACMR)

Reporting relationship: Director
Issuer ticker: ACMR
Reported as of: 19 May 2026
Net transaction value: -$331,111
SEC form: 4
Accepted by SEC: 21 May 2026, 16:30:11 UTC
Prior SEC filing: 11 Mar 2026
Source filing: View source filing
Reporting owner signature: /s/ Mark McKechnie, Attorney-in-Fact for Haiping Dun

Key filing fact

Haiping Dun filed Form 4 for ACM Research, Inc. (ACMR) on 21 May 2026.

Key facts

This page summarizes Haiping Dun's Form 4 filing for ACM Research, Inc. (ACMR).
6 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 21 May 2026, 16:30.

Change

Previous filing in this sequence was filed on 11 Mar 2026.
Current net transaction value: -$331,111.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001721581 Primary reporting owner

Dun Haiping

Relationship: Director
Address: C/O ACM RESEARCH, INC., 42307 OSGOOD ROAD, SUITE I, FREMONT
Signature: /s/ Mark McKechnie, Attorney-in-Fact for Haiping Dun
Signature date: 21 May 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

ACMR transaction

Class A Common Stock

Options Exercise

Transaction value
Shares: +5,000
Change %
Price: $5.60^*
Shares after: 5,000
Date: 19 May 2026
Ownership: Direct

ACMR transaction

Class A Common Stock

Sale

Transaction value: $85,099
Shares: -1,333
Change %: -27%
Price: $63.84
Shares after: 3,667
Date: 19 May 2026
Ownership: Direct
Footnotes: F1, F2

ACMR transaction

Class A Common Stock

Sale

Transaction value: $32,545
Shares: -500
Change %: -14%
Price: $65.09
Shares after: 3,167
Date: 19 May 2026
Ownership: Direct
Footnotes: F1, F3

ACMR transaction

Class A Common Stock

Sale

Transaction value: $87,978
Shares: -1,309
Change %: -41%
Price: $67.21
Shares after: 1,858
Date: 19 May 2026
Ownership: Direct
Footnotes: F1, F4

ACMR transaction

Class A Common Stock

Sale

Transaction value: $125,489
Shares: -1,858
Change %: -100%
Price: $67.54
Shares after: 0
Date: 19 May 2026
Ownership: Direct
Footnotes: F1, F5

ACMR holding

Class A Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 100,000
Date: 19 May 2026
Ownership: Dun Family GST Trust

ACMR holding

Class A Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 755,090
Date: 19 May 2026
Ownership: Haiping Dun & Chi-Pin H Dun Revocable Trust

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

ACMR transaction Derivative

Stock Option

Options Exercise

Transaction value
Shares: -5,000
Change %: -9.1%
Price: $0.000000^*
Shares after: 50,000
Date: 19 May 2026
Ownership: Direct
Underlying class: Class A Common Stock
Underlying amount: 5,000
Exercise price: $5.60
Footnotes: F6

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Rule 10b5-1 trading plan

These transactions were reported as open-market trades under a Rule 10b5-1 plan. The plan lets an insider set trading instructions in advance, which can reduce the risk of trading while in possession of material nonpublic information.

Original filing language: transaction made pursuant to a contract, instruction, or written plan intended to satisfy Rule 10b5-1(c).

Explanation of responses 6 footnotes

Footnote F1

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.

Footnote F2

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.

Footnote F3

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.

Footnote F4

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.

Footnote F5

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.

Footnote F6

The option is fully vested and exercisable.