Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in QUMSU held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | Westchester Capital Management, LLC | 100K | $1.0M | 0.0% | 1.208% | 0.05% |
| 2 | GABELLI & Co INVESTMENT ADVISERS, INC. | 68K | $699K | 0.0% | 0.818% | 0.10% |
| 3 | GABELLI FUNDS LLC | 57K | $591K | 0.0% | 0.692% | 0.00% |
| 4 | Clear Street Group Inc. | 22K | $232K | +51.1% | 0.271% | 0.00% |
| 5 | UBS Group AG | 464 | $5K | +1.1% | 0.006% | 0.00% |
| 6 | HRT FINANCIAL LP | 30K | $304 | -3.1% | 0.364% | 0.00% |
| 7 | GLAZER CAPITAL, LLC | 219 | $2 | — | 0.003% | 0.00% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). “% of Fund” shows how much of that investor’s total 13F portfolio is invested in QUMSU — a direct measure of their conviction.
Filings activity in QUMSU during Q1 2026, grouped by how each filer changed its position.
Institutions that fully closed their QUMSU position in Q1 2026
3 quarters of 13F filings · Δ columns show change vs prior quarter
| Quarter | Inst. Holders | Δ Holders | Ownership % | Δ Ownership | Total 13F Value | Δ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 7 | 22% | 2.96% | 9.82 pp | $3M | 77% |
| Q4 2025 | 9 | 70% | 12.78% | 48.14 pp | $11M | 79% |
| Q3 2025 | 30 | — | 60.92% | — | $52M | — |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Δ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying QUMSU stock.
Based on Q1 2026 13F filings, institutional ownership of Quantumsphere Acquisition Corp. Units stands at 3.0%, held across 7 reporting institutions.
Westchester Capital Management, LLC is the largest reported institutional holder of QUMSU, with approximately 100,000 shares worth $0.00B as of Q1 2026.
No marquee "smart money" managers (Berkshire, Burry, ARK, Tiger Global, Pershing Square, Baupost, etc.) currently appear among the top 25 institutional holders of QUMSU.
Our composite Smart Money Score for QUMSU is 16 out of 100 (Heavy Distribution). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
1 institutions opened new positions in QUMSU during Q1 2026, while 3 fully exited. 4 added to existing positions and 2 trimmed.
QUMSU institutional ownership fell by 9.82 percentage points quarter-over-quarter, with a net change of -2 holders.
The top 10 institutions account for 100.0% of all reported 13F value in QUMSU, and the top 25 account for 100.0%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
Quantumsphere Acquisition Corp. Units (QUMSU) Institutional Ownership