X0306 4 2021-06-17 0 0001555279 908 Devices Inc. MASS 0001237190 ELOI FENEL M C/O 908 DEVICES INC. 645 SUMMER STREET BOSTON MA 02210 1 0 0 0 Stock Option (option to buy) 41.70 2021-06-17 4 A 0 2455 0.00 A 2031-06-17 Common Stock, par value $0.001 2455 2455 D Restricted Stock Unit 2021-06-17 4 A 0 1379 0.00 A Common Stock, par value $0.001 1379 1379 D The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following June 17, 2021, subject to the reporting person's continued service through the applicable vesting date. Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.001, when vested. The RSUs become fully vested on June 17, 2022 or the 2022 Annual Meeting of the Stockholders of 908 Devices Inc., whichever occurs first, subject to the reporting person's continued service through the applicable vesting date, provided that, if the reporting person terminates their service for any reason, then a prorated number of RSUs will vest. The RSUs have no expiration date. /s/ Michael S. Turner, as Attorney-in-Fact 2021-06-21