13D Management LLC — 13F Holdings & Portfolio
CIK 1600133 · latest 13F-HR filed 2026-08-14
13D Management LLC manages $71.3M in 13F-reported U.S. long-equity assets across 11 reported positions as of its 2026-06-30 13F-HR filing. Its largest disclosed positions are VSAT (15.89%), TWLO (11.28%), MRCY (10.37%). Quarter over quarter (versus its 2026-03-31 filing) the fund opened 1 new position and exited 3; 10 existing positions rose in reported value and 0 fell.
AUM is the long-equity portion reported on Form 13F-HR. Excludes short positions, cash, foreign holdings, and non-13F assets. For informational purposes only — not investment advice.
Long-equity book
Distinct positions
Filed 2026-08-14
vs 2026-03-31
Portfolio charts
Latest quarter's book, what changed, and how the portfolio has evolved across filings.
Portfolio map
Q2 26Box size = position value; colour = change in share count vs the prior quarter (green added, red trimmed, blue new). Rows split across managers or share classes are combined. Click a box for the stock.
Sector mix
% of 13F valueSectors from each company's SIC code; funds and ETFs grouped separately.
Biggest buys and sells
Q1 26 → Q2 26Estimated from the change in shares held × the quarter-end price, so price moves alone don't count as buying. New and exited positions are included.
13F assets and positions
4 quartersTotal reported 13F value (bars) and number of positions (line) each quarter. Value changes include market moves.
Top positions over time
reported valueThe eight largest current positions, valued at each quarter end.
Concentration
top 10 = 94.4%Cumulative share of the portfolio held in the largest N positions.
As of the firm’s regulatory filing dated Mar 25, 2026.
16TH FLOOR
NEW YORK, NY 10019
| Name | Title / Status | Ownership | Type |
|---|---|---|---|
| SQUIRE, KENNETH, BRADLEY Control | MANAGING MEMBER AND CHIEF INVESTMENT OFFICER since Mar 2010 | 75% or more | Individual |
| KIM, KI-TAE | CHIEF COMPLIANCE OFFICER AND CHIEF OPERATING OFFICER since Jun 2023 | Less than 5% | Individual |
Ownership & leadership changes · 5 filings with changes since Nov 7, 2011
From the firm’s regulatory filings, newest first. Dates are filing dates: a filing that no longer lists someone does not say when they left.
- AddedKIM, KI-TAE · CHIEF COMPLIANCE OFFICER AND CHIEF OPERATING OFFICER · Less than 5%
- ChangedSQUIRE, KENNETH, BRADLEY · title MANAGING MEMBER AND CHIEF COMPLIANCE OFFICER → MANAGING MEMBER AND CHIEF INVESTMENT OFFICER
- No longer listedKUKULKA, CHARMAGNE, BETH · CHIEF COMPLIANCE OFFICER · Less than 5% · listed since Feb 2022
- ChangedSQUIRE, KENNETH, BRADLEY · title MANAGING MEMBER → MANAGING MEMBER AND CHIEF COMPLIANCE OFFICER
- No longer listedBALDAUFF, NATALIE · CHIEF COMPLIANCE OFFICER · Less than 5% · listed since Jul 2018
- AddedKUKULKA, CHARMAGNE, BETH · CHIEF COMPLIANCE OFFICER · Less than 5%
- No longer listedKOLINSKY, JOSEPH, ROBERT · CHIEF COMPLIANCE OFFICER · Less than 5% · listed since Nov 2015
- AddedBALDAUFF, NATALIE · CHIEF COMPLIANCE OFFICER · Less than 5%
- AddedKOLINSKY, JOSEPH, ROBERT · CHIEF COMPLIANCE OFFICER · Less than 5%
- ChangedSQUIRE, KENNETH, BRADLEY · title MANAGING MEMBER AND CHIEF COMPLIANCE OFFICER → MANAGING MEMBER
- ListedSQUIRE, KENNETH, BRADLEY · MANAGING MEMBER AND CHIEF COMPLIANCE OFFICER · 75% or more · control person
Quarter-over-quarter changes
Changes in reported position value vs the prior 13F, so price moves count too, not just shares bought or sold.
Top Adds (vs prior quarter)
- VIASAT INC$3.8M +50.3%
- MERCURY SYS INC$3.0M +67.8%
- ETSY INC$1.8M +50.7%
- CHARLES RIV LABS INTL INC$1.4M +31.5%
- PEARSON PLC$1.3M +21.0%
13D Management LLC Holdings (2026-06-30)
Rows tagged Call or Put are options positions, not stock. Per SEC Form 13F-HR, Value shows the notional value of the underlying (shares covered × underlying price), not the option premium. Shares is the number of underlying shares covered (divide by 100 for contract count).
| # | Issuer | Symbol | CUSIP | Value | Weight | Shares | Type |
|---|---|---|---|---|---|---|---|
| 1 | VIASAT INC | VSAT | 92552V100 | $11.3M | 15.89% | 126,250 | SH |
| 2 | TWILIO INC | TWLO | 90138F102 | $8.0M | 11.28% | 39,000 | SH |
| 3 | MERCURY SYS INC | MRCY | 589378108 | $7.4M | 10.37% | 60,462 | SH |
| 4 | PEARSON PLC | PSO | 705015105 | $7.3M | 10.21% | 458,338 | SH |
| 5 | AUTOLIV INC | ALV | 052800109 | $6.5M | 9.09% | 55,839 | SH |
| 6 | CHARLES RIV LABS INTL INC | CRL | 159864107 | $5.9M | 8.20% | 25,800 | SH |
| 7 | SYNOPSYS INC | SNPS | 871607107 | $5.6M | 7.91% | 12,650 | SH |
| 8 | EXELIXIS INC | EXEL | 30161Q104 | $5.5M | 7.73% | 101,335 | SH |
| 9 | ETSY INC | ETSY | 29786A106 | $5.4M | 7.59% | 71,836 | SH |
| 10 | INTEGER HLDGS CORP | ITGR | 45826H109 | $4.4M | 6.16% | 47,000 | SH |
| 11 | SIX FLAGS ENTERTAINMENT CORP | FUN | 83001C108 | $4.0M | 5.57% | 186,500 | SH |
| Period | Filed | AUM | Holdings | Accession |
|---|---|---|---|---|
| 2026-06-30 | 2026-08-14 | $71.3M | 11 | 0001172661-26-003515 |
| 2026-03-31 | 2026-05-15 | $64.5M | 13 | 0001172661-26-002041 |
| 2025-12-31 | 2026-02-17 | $84.0M | 16 | 0001172661-26-000830 |
| 2025-09-30 | 2025-11-14 | $104.3M | 18 | 0001172661-25-004791 |
16TH FLOOR
NEW YORK, NY 10019