X0202 SCHEDULE 13G/A 0001072613-21-000077 0001402439 XXXXXXXX LIVE 5 Common Stock par value $0.001 per share 03/31/2026 0001555279 908 Devices Inc. 65443P102 44 Third Avenue Burlington MA 01803 Rule 13d-1(d) ARCH Venture Fund VII, L.P. DE 0 5725045 0 5725045 5725045 N 15.1 PN ARCH Venture Partners VII, L.P. DE 0 5725045 0 5725045 5725045 N 15.1 PN ARCH Venture Partners VII, LLC DE 0 5725045 0 5725045 5725045 N 15.1 OO Keith Crandell X1 84171 5725045 84171 5725045 5809216 N 15.3 IN Clinton Bybee X1 0 5725045 0 5725045 5725045 N 15.1 IN Robert Nelsen X1 0 5725045 0 5725045 5725045 N 15.1 IN 908 Devices Inc. 44 Third Avenue, Burlington, MA 01803 ARCH Venture Fund VII, L.P. ("ARCH Venture Fund VII"); ARCH Venture Partners VII, L.P. ("AVP VII LP"); ARCH Venture Partners VII, LLC ("AVP VII LLC") (collectively, the "Reporting Entities" and individually, each a "Reporting Entity"); and Keith Crandell ("Crandell"), Robert Nelsen ("Nelsen") and Clinton Bybee ("Bybee") (collectively, the "Managing Directors" and individually, each a "Managing Director"). The Reporting Entities and the Managing Directors collectively are referred to as the "Reporting Persons". The Reporting Persons are filing this report with respect to shares of Common Stock, par value $0.001 per share (the "Common Stock") of 908 Devices Inc. (the "Issuer"). 8755 W. Higgins Avenue, Suite 1025, Chicago, IL 60631 ARCH Venture Fund VII and AVP VII LP are limited partnerships organized under the laws of the State of Delaware. AVP VII LLC is a limited liability company organized under the laws of the State of Delaware. Each Managing Director is a US citizen. Y ARCH Venture Fund VII is the record owner of 5,725,045 shares of Common Stock (the "Record Shares") as of March 31, 2026. AVP VII LP, as the sole general partner of ARCH Venture Fund VII, may be deemed to beneficially own the Record Shares. AVP VII LLC, as the sole general partner of AVP VII, may be deemed to beneficially own the Record Shares. As managing directors of AVP VII LLC, each Managing Director may also be deemed to share the power to direct the disposition and vote of the Record Shares. In addition, as of March 31, 2026, Crandell is a holder of vested options to purchase 57,794 shares of Common Stock (the "Vested Option Shares"), 25,291 fully vested restricted stock units ("RSUs"), and options to purchase 1,086 shares of Common Stock vesting within sixty days (the "Unvested Option Shares"). The information required by Item 4(b) is incorporated by reference to Row 11 of the cover pages hereto. The percentage set forth on the cover sheet for each Reporting Person is based upon 37,813,621 shares of Common Stock outstanding as of May 4, 2026, as reported on the Issuer's Quarterly Report on Form 10-Q as filed with the Securities and Exchange Commission on May 6, 2026, and in the case of Crandell, assumes the issuance of the Vested Option Shares, shares underlying the RSUs, and the Unvested Option Shares. Each Reporting Person disclaims beneficial ownership of such shares of Common Stock except for the shares, if any, such Reporting Person holds of record. See row 11 of the cover pages. See row 5 of the cover pages. See row 6 of the cover pages. See row 7 of the cover pages. See row 8 of the cover pages. Y Y Y Y Y Y ARCH Venture Fund VII, L.P. /s/ ARCH Venture Partners VII, L.P. 05/15/2026 ARCH Venture Partners VII, LLC 05/15/2026 /s/ Mark McDonnell* 05/15/2026 ARCH Venture Partners VII, L.P. /s/ ARCH Venture Parnters VII, LLC 05/15/2026 /s/ Mark McDonnell* 05/15/2026 ARCH Venture Partners VII, LLC /s/ Mark McDonnell* 05/15/2026 Keith Crandell /s/ Mark McDonnell* 05/15/2026 Clinton Bybee /s/ Mark McDonnell* 05/15/2026 Robert Nelsen /s/ Mark McDonnell* 05/15/2026 * This Schedule 13G was executed by Mark McDonnell pursuant to Powers of Attorney dated May 7, 2013 and July 26, 2017, filed as Exhibit 2.0 and Exhibit 2.1 to the Schedule 13G filed with the Securities and Exchange Commission on February 14, 2019 and incorporated herein by reference.