X0206 3 2017-12-06 0 0001503274 Quanterix Corp QTRX 0001205236 WALT DAVID R C/O QUANTERIX CORPORATION, 113 HARTWELL AVENUE LEXINGTON MA 02421 1 0 0 0 Common Stock 396701 D Series A-1 Preferred Stock Common Stock 32959 D Series A-2 Preferred Stock Common Stock 86517 D Series B Preferred Stock Common Stock 334985 D Series C Preferred Stock Common Stock 28691 D Series D Preferred Stock Common Stock 135647 D Reflects the 1-for-3.214 reverse stock split of the Issuer's common stock effected on December 4, 2017 in connection with the Issuer's initial public offering. These shares are convertible into the Issuer's common stock in accordance with the Issuer's Restated Certificate of Incorporation, as amended, at any time after the issuance of such shares, at the holder's election. Not applicable. The shares of preferred stock will convert into common stock immediately prior to the closing of the Issuer's initial public offering using a calculation defined in the Issuer's Restated Certificate of Incorporation, as amended, based on the initial purchase price and the conversion rate in effect at the time of conversion. The shares of preferred stock will convert on a 1-for-3.214 basis and such conversion rate is reflected in the amount of common stock underlying the security. Exhibit 24.1 - Power of Attorney /s/ Brian Keane, Attorney-in-fact 2017-12-06