Mainsail Management Company, LLC
- SEC CIK
- 0001883367
- Latest filing
- Nov 6, 2025
The latest 13F from Mainsail Management Company, LLC covers Q3 2025 (filed Nov 6, 2025): 1 long positions worth $66.0M. The top 10 holdings make up 100.0% of the portfolio, and the largest is Brilliant Earth Group, Inc. (BRLT) at 100.0%. Livermore has 13 filings on Form 13F from this institution, going back to Q4 2022.
What changed in Q3 2025
Share counts compared with Q2 2025: how many positions were new, added to, reduced or sold out, and the biggest buys and sells. Dollar amounts are estimated at the quarter-end prices implied by the filing.
- New
- 0
- Added
- 0
- Reduced
- 0
- Sold out
- 1
- Est. −$22.1M
Biggest buys
New and added positions, by estimated amount bought
None this quarter.
Largest weight increases
New and added positions, by percentage points of the portfolio gained
None this quarter.
Metrics
13F metrics for Q3 2025, computed only from the numbers in the filings. Definitions below.
- Portfolio value
- $66.0M
- −$63.8K (−0.1%) vs. prior quarter
- Positions
- 1
- −1 vs. prior quarter
- Top 10 concentration
- 100.0%
- Top 10 as share of value
- Turnover
- 0.0%
- Q3 2025, one quarter
- Average holding period
- 12.0 quarters
- Weighted by value
How these are calculated
- Portfolio value: the market value of all long positions in the 13F, as reported at quarter end, excluding options.
- Top 10 concentration: the combined value of the 10 largest positions as a share of portfolio value.
- Turnover: the smaller of this quarter's estimated purchases and estimated sales, divided by the average of this and last quarter's portfolio value. Estimates multiply the change in shares by the quarter-end price implied by the filing (market value divided by shares); new positions use this quarter's value and sold-out positions last quarter's. Only positions reported in shares count, and it is not calculated when the previous quarter was not filed.
- Average holding period: how many consecutive quarters each current position has been held (including this one; a quarter without the position or without a filing starts the count over), weighted by this quarter's value. Counting starts with the first 13F in Livermore (Q4 2022), so positions held before then are understated.
13F filings by quarter
12 quarters, going back to Q4 2022. Bars show each quarter's 13F portfolio value; quarters without a filing are left blank.
Peak $141.6M (Q4 2022)
| Quarter | Filed | Positions | Value | Top 3 holdings | Changes | Filing |
|---|---|---|---|---|---|---|
| Q3 2025 | Nov 6, 2025 | 1 | $66.0M | BRLT | vs. Q2 2025 | SEC |
| Q2 2025 | Aug 4, 2025 | 2 | $66.1M | BRLTTTAN | vs. Q1 2025 | SEC |
| Q1 2025 | May 13, 2025 | 3 | $84.6M | BRLTTTANSSTI | vs. Q4 2024 | SEC |
| Q4 2024 | May 13, 2025Amended | 3 | $103.5M | BRLTTTANSSTI | vs. Q3 2024 | SECSEC |
| Q3 2024 | Nov 13, 2024 | 2 | $69.3M | BRLTSSTI | vs. Q2 2024 | SEC |
| Q2 2024 | Aug 12, 2024 | 2 | $71.9M | BRLTSSTI | vs. Q1 2024 | SEC |
| Q1 2024 | May 7, 2024 | 2 | $96.8M | BRLTSSTI | vs. Q4 2023 | SEC |
| Q4 2023 | Feb 12, 2024 | 2 | $121.0M | BRLTSSTI | vs. Q3 2023 | SEC |
| Q3 2023 | Nov 7, 2023 | 2 | $95.9M | BRLTSSTI | vs. Q2 2023 | SEC |
| Q2 2023 | Aug 14, 2023 | 2 | $126.0M | BRLTSSTI | vs. Q1 2023 | SEC |
| Q1 2023 | May 12, 2023 | 2 | $128.6M | BRLTSSTI | vs. Q4 2022 | SEC |
| Q4 2022 | Feb 14, 2023 | 2 | $141.6M | BRLTSSTI | – | SEC |
13D and 13G filings
Companies where Mainsail Management Company, LLC reports owning 5% or more on Schedule 13D or 13G, and its latest filings.
Current stakes of 5% or more
1 company, largest stake first.
Latest filings
1 filing on file made by Mainsail Management Company, LLC or listing it as a reporting person, newest first.