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WESTFIELD CAPITAL MANAGEMENT CO LP: MKSI position timeline

Available 13F reports, 13D and 13G stakes and each Form 3, 4 and 5 line of WESTFIELD CAPITAL MANAGEMENT CO LP on MKSI, newest first. How the timeline and the estimate are built.

WESTFIELD CAPITAL MANAGEMENT CO LP held 928,617 MKSI shares at 2026-06-30 per its 13F-HR filed 2026-08-12.

the latest 13F is the newest step

  1. period ended2026-06-30
    13F 928,617 shares
    Change vs previous 13F -118,146 shares

    1.35% of the 13F portfolio, value $413,048,645.

    13F-HR 0001177719-26-000021 filed by WESTFIELD CAPITAL MANAGEMENT CO LP
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  2. period ended2026-03-31
    13F 1,046,763 shares
    Change vs previous 13F +206,990 shares

    1.01% of the 13F portfolio, value $240,556,578.

    13F-HR 0001177719-26-000018 filed by WESTFIELD CAPITAL MANAGEMENT CO LP
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  3. period ended2025-12-31
    13F 839,773 shares
    Change vs previous 13F +516,409 shares

    0.56% of the 13F portfolio, value $134,195,725.

    13F-HR 0001177719-26-000005 filed by WESTFIELD CAPITAL MANAGEMENT CO LP
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  4. period ended2025-09-30
    13F 323,364 shares
    Change vs previous 13F +323,364 shares

    0.17% of the 13F portfolio, value $40,022,762.

    13F-HR 0001177719-25-000003 filed by WESTFIELD CAPITAL MANAGEMENT CO LP
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  5. period ended2024-12-31
    13F 0 shares
    Change vs previous 13F -24,100 shares

    13F-HR 0001085146-25-000986 filed by WESTFIELD CAPITAL MANAGEMENT CO LP
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

    Exited: the 13F for this period no longer lists the position.

  6. period ended2024-09-30
    13F 24,100 shares
    Change vs previous 13F not available

    0.01% of the 13F portfolio, value $2,619,911.

    13F-HR 0001085146-24-005556 filed by WESTFIELD CAPITAL MANAGEMENT CO LP
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).