Initial Statement of Beneficial Ownership (Form 3)

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * McCallion Kevin J. 2. Date of Event Requiring Statement (Month/Day/Year) 02/26/2026 3. Issuer Name and Ticker or Trading Symbol 908 Devices Inc. [MASS] (Last) (First) (Middle) C/O 908 DEVICES INC., 44 3RD AVENUE 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) SVP, Products and Production 5. If Amendment, Date Original Filed (Month/Day/Year) (Street) BURLINGTON, MA 01803 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock 44,925 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (right to buy)	(1)	08/27/2030	Common Stock	26,693	$1.05	D
Stock Option (right to buy)	(1)	03/01/2032	Common Stock	27,917	$16.66	D
Stock Option (right to buy)	(2)	02/28/2033	Common Stock	37,801	$8.83	D
Stock Option (right to buy)	(3)	02/28/2034	Common Stock	42,014	$7.35	D
Stock Option (right to buy)	(4)	03/02/2035	Common Stock	40,011	$1.98	D
Stock Option (right to buy)	(5)	02/01/2036	Common Stock	21,187	$6.19	D
Restricted Stock Units	(6)	(6)	Common Stock	6,229	(7)	D
Restricted Stock Units	(8)	(8)	Common Stock	15,376	(7)	D
Restricted Stock Units	(8)	(8)	Common Stock	58,602	(7)	D
Restricted Stock Units	(9)	(9)	Common Stock	48,466	(7)	D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
McCallion Kevin J. C/O 908 DEVICES INC. 44 3RD AVENUE BURLINGTON, MA 01803			SVP, Products and Production

Signatures

/s/ Mark S. Levine, Attorney-in-Fact		03/04/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(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).
(1)	The shares underlying the option are fully vested and immediately exercisable.
(2)	Twenty-five percent of the shares underlying the option became vested and exercisable on February 1, 2024, and the remaining 75% of the shares underlying the option became or will become vested and exercisable in substantially equal monthly installments over the 36 months following February 1, 2024, subject to the reporting person's continued service through the applicable vesting date.
(3)	Twenty-five percent of the shares underlying the option became vested and exercisable on February 1, 2025, and the remaining 75% of the shares underlying the option became or will become vested and exercisable in substantially equal monthly installments over the 36 months following February 1, 2025, subject to the reporting person's continued service through the applicable vesting date.
(4)	One-third of the shares underlying the option became vested and exercisable on February 1, 2026, and the remaining two-thirds of the shares underlying the option became or will become vested and exercisable in substantially equal monthly installments over the 24 months following February 1, 2026, subject to the reporting person's continued service through the applicable vesting date.
(5)	One-third of the shares underlying the option become vested and exercisable on February 1, 2027, and the remaining two-thirds of the shares underlying the option become vested and exercisable in substantially equal monthly installments over the 24 months following February 1, 2027, subject to the reporting person's continued service through the applicable vesting date.
(6)	These restricted stock units ("RSUs") vest on February 1, 2027, subject to the reporting person's continued service through the applicable vesting date. The RSUs have no expiration date.
(7)	Each RSU represents a contingent right to receive one share of Common Stock, par value $0.001, when vested.
(8)	These RSUs vest in two substantially equal annual installments at the two anniversary dates following February 1, 2026, subject to the reporting person's continued service through the applicable vesting date. The RSUs have no expiration date.
(9)	These RSUs vest in three substantially equal annual installments at the three anniversary dates following February 1, 2026, subject to the reporting person's continued service through the applicable vesting date. The RSUs have no expiration date.

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