AWM trims 50,000-share stake in 908 Devices Inc. (MASS) stock

Rhea-AI Filing Summary

908 Devices Inc. (MASS) reports that AWM Investment Company, Inc., a ten percent owner, indirectly sold 50,000 shares of common stock in open-market transactions on August 20–21, 2026. The sales, executed through limited partnerships advised by AWM, occurred at weighted average prices of about $10.52–$10.61 per share.

AWM is investment adviser to several Special Situations funds and has sole voting and investment power over large share blocks they hold. AWM disclaims beneficial ownership of these shares except to the extent of its pecuniary interest.

Insider Trade Summary

Net Seller: 50,000 shares

Net Sell 2 txns

Insider AWM Investment Company, Inc.

Role 10% Owner

Sold 50,000 shs ($530K)

Type	Security	Shares	Price	Value
Sale	Common Stock F2, F3, F1	41,578	$10.6104	$441K
Sale	Common Stock F1	8,422	$10.5246	$89K

Holdings After Transaction: Common Stock — 4,779,773 shares (Indirect, By Limited Partnership)

Footnotes (3)

1. F1. This is a weighted average price.
2. F2. AWM Investment Company, Inc., a Delaware Corporation (AWM), is the investment adviser to Special Situations Fund III QP, L.P. (SSFQP), Special Situations Cayman Fund, L.P. (CAY), Special Situations Private Equity Fund, L.P. (SSPE), Special Situations Technology Fund, L.P. (TECH) and Special Situations Technology Fund II, L.P. (TECH II and together with SSFQP, CAY, SSPE and TECH, the Funds). As the investment adviser to the Funds, AWM holds sole voting and investment power over 1,981,785 shares of Common Stock of the Issuer (the Shares) held by SSFQP, 565,726 Shares held by CAY, 216,802 Shares held by SSPE, 338,137 Shares held by TECH and 1,677,323 Shares held by TECH II.
3. F3. David M. Greenhouse (Greenhouse) and Adam C. Stettner (Stettner) are the controlling principals of AWM. The reporting person disclaims beneficial ownership of the Shares, except to the extent of its pecuniary interest therein. This report shall not be deemed an admission that the reporting person is the beneficial owner of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

Key Figures

Shares sold on 2026-08-21: 41,578 shares of Common Stock Weighted average sale price on 2026-08-21: $10.6104 per share Shares sold on 2026-08-20: 8,422 shares of Common Stock +4 more

7 metrics

Shares sold on 2026-08-21 41,578 shares of Common Stock Indirect sale by limited partnership at a weighted average price

Weighted average sale price on 2026-08-21 $10.6104 per share Sale of 41,578 indirectly held MASS shares

Shares sold on 2026-08-20 8,422 shares of Common Stock Indirect sale by limited partnership at a weighted average price

Weighted average sale price on 2026-08-20 $10.5246 per share Sale of 8,422 indirectly held MASS shares

Total net shares sold 50,000 shares of Common Stock Aggregate of two indirect open-market sales reported in the Form 4

Shares with voting and investment power (SSFQP) 1,981,785 shares of Common Stock Held by Special Situations Fund III QP, L.P., over which AWM has sole voting and investment power

Shares with voting and investment power (TECH II) 1,677,323 shares of Common Stock Held by Special Situations Technology Fund II, L.P., over which AWM has sole voting and investment power

Key Terms

weighted average price, pecuniary interest, beneficial ownership, Section 16 of the Securities Exchange Act of 1934

4 terms

weighted average price financial

"This 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.

pecuniary interest financial

"disclaims beneficial ownership of the Shares, except to the extent of its pecuniary interest"

beneficial ownership regulatory

"shall not be deemed an admission that the reporting person is the beneficial owner"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

Section 16 of the Securities Exchange Act of 1934 regulatory

"for purposes of Section 16 of the Securities Exchange Act of 1934, as amended"

A provision of federal securities law that requires company insiders—directors, officers and large shareholders—to publicly report their stock holdings and trades and to surrender any “short-swing” profits from purchases and sales within a six-month window. It acts like a rule that forces leaders to announce their trades and prevents quick buy-sell windfalls, giving investors transparency into insider activity and reducing opportunities for unfair gain.

FAQ

What insider transactions were reported for 908 Devices Inc. (MASS)?

The filing reports that AWM Investment Company, Inc. indirectly sold a total of 50,000 shares of 908 Devices Inc. common stock in open-market transactions on August 20–21, 2026, through limited partnerships it advises.

At what prices were the MASS shares sold in this Form 4?

The reported sales of MASS common stock occurred at weighted average prices of $10.6104 per share on August 21, 2026 and $10.5246 per share on August 20, 2026, as disclosed in the Form 4 footnotes.

Who is the reporting person in this MASS Form 4 filing?

The reporting person is AWM Investment Company, Inc., which is identified as a ten percent owner of 908 Devices Inc. and serves as investment adviser to several Special Situations funds that hold MASS common stock.

Are the MASS shares held directly by AWM Investment Company, Inc.?

No. The MASS shares are held indirectly through several Special Situations limited partnerships. AWM is the investment adviser with sole voting and investment power over those shares and reports indirect ownership "By Limited Partnership."

How many MASS shares are under AWM’s voting and investment power through the funds?

AWM has sole voting and investment power over 1,981,785 shares held by SSFQP, 565,726 shares held by CAY, 216,802 shares held by SSPE, 338,137 shares held by TECH, and 1,677,323 shares held by TECH II.

Does AWM claim full beneficial ownership of the MASS shares reported?

No. AWM disclaims beneficial ownership of the reported MASS shares except to the extent of its pecuniary interest, stating that the report should not be deemed an admission of beneficial ownership for Section 16 or any other purpose.

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Available on EDGAR 08/24/2026 - 04:51 PM Accepted by SEC EDGAR 08/24/2026 - 04:50 PM Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED 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).

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^*

AWM Investment Company, Inc.

(Last) (First) (Middle)

527 MADISON AVENUE

SUITE 2600

(Street)

NEW YORK NEW YORK 10022

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
908 Devices Inc. [ MASS ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/20/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form 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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	08/20/2026		S		8,422	D	$10.5246(1)	4,821,351	I	By Limited Partnership
Common Stock	08/21/2026		S		41,578(2)(3)	D	$10.6104(1)	4,779,773(2)(3)	I(2)(3)	By Limited Partnership(2)(3)

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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. This is a weighted average price.

2. AWM Investment Company, Inc., a Delaware Corporation (AWM), is the investment adviser to Special Situations Fund III QP, L.P. (SSFQP), Special Situations Cayman Fund, L.P. (CAY), Special Situations Private Equity Fund, L.P. (SSPE), Special Situations Technology Fund, L.P. (TECH) and Special Situations Technology Fund II, L.P. (TECH II and together with SSFQP, CAY, SSPE and TECH, the Funds). As the investment adviser to the Funds, AWM holds sole voting and investment power over 1,981,785 shares of Common Stock of the Issuer (the Shares) held by SSFQP, 565,726 Shares held by CAY, 216,802 Shares held by SSPE, 338,137 Shares held by TECH and 1,677,323 Shares held by TECH II.

3. David M. Greenhouse (Greenhouse) and Adam C. Stettner (Stettner) are the controlling principals of AWM. The reporting person disclaims beneficial ownership of the Shares, except to the extent of its pecuniary interest therein. This report shall not be deemed an admission that the reporting person is the beneficial owner of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

	Adam Stettner	08/24/2026
	** Signature of Reporting Person	Date
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)