AWM Investment Company reports 11.8% 908 Devices (MASS) ownership through Special Situations funds

Rhea-AI Filing Summary

908 Devices Inc. received an updated ownership report from AWM Investment Company, Inc., an investment adviser to several Special Situations funds. AWM reported beneficial ownership of 4,879,773 shares of 908 Devices common stock, representing 11.8% of the outstanding class as of this filing.

AWM has sole voting and dispositive power over these shares, which are held across multiple funds: 577,077 shares by Special Situations Cayman Fund, 2,020,434 by Special Situations Fund III QP, 266,802 by Special Situations Private Equity Fund, 338,137 by Special Situations Technology Fund, and 1,677,323 by Special Situations Technology Fund II. Control of AWM and the funds’ general partners is described as resting with principals David M. Greenhouse and Adam C. Stettner.

Key Figures

Beneficial ownership: 4,879,773 shares Percent of class: 11.8% Cayman fund holdings: 577,077 shares +4 more

7 metrics

Beneficial ownership 4,879,773 shares Shares of 908 Devices common stock beneficially owned by AWM

Percent of class 11.8% Percentage of 908 Devices common stock class reported by AWM

Cayman fund holdings 577,077 shares Shares held by Special Situations Cayman Fund, L.P.

SSFQP holdings 2,020,434 shares Shares held by Special Situations Fund III QP, L.P.

SSPE holdings 266,802 shares Shares held by Special Situations Private Equity Fund, L.P.

TECH holdings 338,137 shares Shares held by Special Situations Technology Fund, L.P.

TECH II holdings 1,677,323 shares Shares held by Special Situations Technology Fund II, L.P.

Key Terms

beneficially owned, sole voting power, sole dispositive power, investment adviser, +1 more

5 terms

beneficially owned financial

"Item 4. | Ownership (a) | Amount beneficially owned: 4,879,773"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole voting power financial

"5 | Sole Voting Power 4,879,773.00 6 | Shared Voting Power"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

sole dispositive power financial

"7 | Sole Dispositive Power 4,879,773.00 8 | Shared Dispositive Power"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

investment adviser financial

"AWM Investment Company, Inc. ... is the investment adviser to Special Situations"

An investment adviser is a person or firm that professionally manages money and gives recommendations about buying, selling, or holding investments. Like a financial coach or guide, they have a legal duty to act in a client's best financial interest, so their advice, fees and potential conflicts can directly affect returns and risk — making their role important for investors who want informed, accountable help with portfolios.

percent of class financial

"(b) | Percent of class: 11.8 %"

Percent of class is the portion of a specific category of securities—such as a company’s common shares, preferred shares, or a bond series—that takes part in or approves a corporate action (vote, consent, tender, etc.). Investors watch this number because it reveals how much support or opposition exists within that particular shareholder group; like counting how many members of a club back a proposal, it can determine whether a plan passes or how influence is distributed.

FAQ

What stake in 908 Devices Inc. (MASS) does AWM Investment Company report?

AWM Investment Company reports beneficial ownership of 4,879,773 shares of 908 Devices common stock, representing 11.8% of the outstanding class. These shares are held across multiple Special Situations funds it advises.

Who is the reporting person in this Schedule 13G/A for 908 Devices Inc. (MASS)?

The reporting person is AWM Investment Company, Inc., a Delaware corporation acting as investment adviser to several Special Situations funds. It reports voting and investment power over shares of 908 Devices held by those funds.

How are AWM’s 4,879,773 MASS shares allocated among its funds?

AWM reports sole power over 577,077 shares held by Cayman, 2,020,434 by SSFQP, 266,802 by SSPE, 338,137 by TECH, and 1,677,323 by TECH II. Together these positions total 4,879,773 shares.

Does AWM have sole or shared voting power over its MASS holdings?

AWM reports sole voting power over 4,879,773 shares of 908 Devices and no shared voting power. It likewise reports sole dispositive power over the same number of shares, with no shared dispositive power.

Who controls AWM and the Special Situations funds holding MASS shares?

The filing states that David M. Greenhouse and Adam C. Stettner are controlling principals of AWM and members of the various general partners of the Special Situations funds that hold 908 Devices shares.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/14/2026 - 02:58 PM Accepted by SEC EDGAR 08/14/2026 - 02:58 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

908 Devices Inc.

(Name of Issuer)

Common Stock, Par Value $0.001

(Title of Class of Securities)

65443P102

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 65443P102

1

Names of Reporting Persons

AWM Investment Company, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 4,879,773.00
6	Shared Voting Power
7	Sole Dispositive Power 4,879,773.00
8	Shared Dispositive Power

9

Aggregate Amount Beneficially Owned by Each Reporting Person

4,879,773.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

11.8 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: AWM Investment Company, Inc., a Delaware corporation (AWM), is the investment adviser to Special Situations Cayman Fund, L.P. (CAYMAN), Special Situations Fund III QP, L.P. (SSFQP), 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) (CAYMAN, SSFQP, SSPE, TECH and TECH II will hereafter be referred to as the Funds). As the investment adviser to the Funds, AWM holds sole voting and investment power over 577,077 shares of Common Stock of the Issuer (the Shares) held by CAYMAN, 2,020,434 Shares held by SSFQP, 266,802 Shares held by SSPE, 338,137 Shares held by TECH and 1,677,323 Shares held by TECH II

SCHEDULE 13G

Item 1.
(a)	Name of issuer: 908 Devices Inc.
(b)	Address of issuer's principal executive offices: 44 THIRD AVENUE, BURLINGTON, MASSACHUSETTS, 01803
Item 2.
(a)	Name of person filing: The person filing this report is AWM Investment Company, Inc., a Delaware corporation (AWM), which is the investment adviser to Special Situations Cayman Fund, L.P., a Cayman Island limited partnership (CAYMAN), Special Situations Fund III QP, L.P., a Delaware limited partnership (SSFQP) Special Situations Private Equity Fund, L.P., a Delaware limited partnership (SSPE), Special Situations Technology Fund, L.P., a Delaware limited partnership (TECH) and Special Situations Technology Fund II, L.P., a Delaware limited partnership (TECH II). The principal business of each Fund is to invest in equity and equity-related securities and other securities of any kind or nature. David M. Greenhouse (Greenhouse) and Adam C. Stettner (Stettner) are members of SSCayman, L.L.C., a Delaware limited liability company (SSCAY), the general partner of CAYMAN. Greenhouse and Stettner are members of: MGP Advisers Limited Partnership, a Delaware limited partnership (MGP), the general partner of SSFQP; MG Advisers, L.L.C., a New York limited liability company (MG), the general partner of SSPE; and SST Advisers, L.L.C., a Delaware limited liability company (SSTA), the general partner of TECH and TECH II. Greenhouse and Stettner are also controlling principals of AWM.
(b)	Address or principal business office or, if none, residence: The principal business address for AWM is c/o Special Situations Funds, 527 Madison Avenue, Suite 2600, New York, NY 10022
(c)	Citizenship: AWM is a Delaware Corporation
(d)	Title of class of securities: Common Stock, Par Value $0.001
(e)	CUSIP No.: 65443P102
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 4,879,773
(b)	Percent of class: 11.8 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: AWM is the investment adviser to each of the Funds. As the investment adviser to the Funds, AWM holds sole voting power over 577,077 shares of Common Stock of the Issuer (the Shares) held by CAYMAN, 2,020,434 Shares held by SSFQP, 266,802 Shares held by SSPE, 338,137 Shares held by TECH and 1,677,323 Shares held by TECH II. Greenhouse and Stettner are members of SSCAY, the general partner of CAYMAN. Greenhouse and Stettner are members of: MGP, the general partner of SSFQP; MG, the general partner of SSPE and SSTA, the general partner of TECH and TECH II. Greenhouse and Stettner are also controlling principals of AWM.
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: AWM is the investment adviser to each of the Funds. As the investment adviser to the Funds, AWM holds sole and investment power over 577,077 shares of Common Stock of the Issuer (the Shares) held by CAYMAN, 2,020,434 Shares held by SSFQP, 266,802 Shares held by SSPE, 338,137 Shares held by TECH and 1,677,323 Shares held by TECH II. Greenhouse and Stettner are members of SSCAY, the general partner of CAYMAN. Greenhouse and Stettner are members of: MGP, the general partner of SSFQP; MG, the general partner of SSPE and SSTA, the general partner of TECH and TECH II. Greenhouse and Stettner are also controlling principals of AWM.
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

AWM Investment Company, Inc.

Signature:	Adam Stettner
Name/Title:	Executive Vice President
Date:	08/14/2026