# INVESTMENT MANAGERS SER TR I (MDBX)

> Institutional ownership reported to the SEC as of Q1 2026, from Form 13F filings. Source: https://holderbook.com/stocks/MDBX/

- Reporting holders: 4
- Reported value: $462.7K
- Held through calls: 0.0%
- Held through puts: 0.0%

A 13F reports long US equity positions only. Shorts, bonds, foreign listings and cash are not visible here, and positions are disclosed up to 45 days after the quarter ends.

## Largest holders

| Manager | Value | Shares | Share of their book | Quarters held |
|---|---|---|---|---|
| [Optiver Holding B.V.](https://holderbook.com/funds/1859606-optiver-holding-b-v/) | $449.8K | 23,185 | 0.0% | 2 |
| [SIMPLEX TRADING, LLC](https://holderbook.com/funds/1488542-simplex-trading-llc/) | $7.9K | 406 | 0.0% | 1 |
| [GROUP ONE TRADING LLC](https://holderbook.com/funds/932540-group-one-trading-llc/) | $5.1K | 261 | 0.0% | 2 |
| [CITIGROUP INC](https://holderbook.com/funds/831001-citigroup-inc/) | $19 | 1 | 0.0% | 2 |

## Quarter by quarter

| Quarter | Holders | Reported value |
|---|---|---|
| Q1 2026 | 4 | $462.7K |
| Q4 2025 | 6 | $1.8M |
| Q3 2025 | 1 | $3.0K |