A Form 4 filed on August 20, 2026 reports that Glenn P. Muir, a director of Cytek Biosciences, Inc. (NASDAQ:CTKB), acquired 3,086 shares of common stock on August 18, 2026 through the vesting of restricted stock units.

Key Highlights

  • Reporting person: Glenn P. Muir, identified as a Director of Cytek Biosciences, Inc.
  • Transaction date: August 18, 2026, with transaction code M (conversion of derivative security).
  • Shares acquired: 3,086 shares of common stock acquired via RSU vesting, held directly.
  • RSU price: The derivative security was acquired at $0, as disclosed in the filing.
  • Remaining RSUs: 52,469 derivative securities (RSUs) remain beneficially owned following the reported transaction.
  • Vesting schedule: The RSU Award vests over 3 years under a detailed fractional schedule tied to specific dates.

Director RSU Conversion and Vesting Details for Cytek Biosciences

According to the filing, Glenn P. Muir, a Director of Cytek Biosciences, Inc., reported the vesting and conversion of restricted stock units into 3,086 shares of the company's common stock on August 18, 2026. The transaction was recorded under transaction code M, indicating the conversion of a derivative security. Each restricted stock unit, as the filing explains, "represents a contingent right to receive one share of the Issuer's common stock."

The filing discloses that the RSU Award vests over 3 years according to a fractional schedule: 2/36 of the total shares vested on August 18, 2026; 3/36 vest on November 18, 2026 and each November 18 thereafter; 4/36 vest on March 10, 2027 and each March 10 thereafter; 3/36 vest on May 18, 2027 and each May 18 thereafter; and 3/36 vest on August 18, 2027 and each August 18 thereafter. The price of the derivative security at conversion is reported as $0.

Following the reported transaction, Muir directly holds 3,086 shares of common stock and retains 52,469 RSUs beneficially owned directly, according to the filing. The form was signed by Gordon Ho as Attorney-in-Fact and filed on August 20, 2026.

What Was Disclosed

The filing reports the conversion of 3,086 restricted stock units into common stock by Cytek Biosciences Director Glenn P. Muir on August 18, 2026, with 52,469 RSUs remaining and a multi-year vesting schedule continuing through 2027 and beyond.