Fastenal Company
MX ˙ BMV ˙ US3119001044
SecurityMX:FAST / Fastenal Company
InstitutionCastleark Management Llc
Latest Disclosed Ownership148,690 shares
Latest Disclosed Value $ 6,899,216
Castleark Management Llc reports 2,048.70% increase in ownership of FAST / Fastenal Company

On May 15, 2026 - Castleark Management Llc filed a 13F-HR form disclosing ownership of 148,690 shares of Fastenal Company (MX:FAST) valued at $6,899,216 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 6,920 shares of Fastenal Company. This represents a change in shares of 2,048.70% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F FASTENAL COM 311900104 148,690 141,770 2,048.70 6,899 2,390.61 0.2283
2026-02-12 2025-12-31 13F FASTENAL COM 311900104 6,920 -122,900 -94.67 278 -95.65 0.0082
2025-11-17 2025-09-30 13F FASTENAL COM 311900104 129,820 122,900 1,776.01 6,366 2,095.17 0.1785
2025-08-18 2025-06-30 13F FASTENAL COM 311900104 6,920 3,460 100.00 291 8.21 0.0087
2025-05-15 2025-03-31 13F FASTENAL COM 311900104 3,460 0 0.00 268 8.06 0.0093
2025-02-18 2024-12-31 13F FASTENAL COM 311900104 3,460 0 0.00 249 0.40 0.0087
2024-11-15 2024-09-30 13F FASTENAL COM 311900104 3,460 0 0.00 247 13.82 0.0101
2024-08-14 2024-06-30 13F FASTENAL COM 311900104 3,460 0 0.00 217 -18.42 0.0089
2024-05-16 2024-03-31 13F FASTENAL COM 311900104 3,460 0 0.00 267 18.75 0.0111
2024-02-15 2023-12-31 13F FASTENAL COM 311900104 3,460 0 0.00 224 18.52 0.0099
2023-11-15 2023-09-30 13F FASTENAL COM 311900104 3,460 0 0.00 189 -7.35 0.0096
2023-08-16 2023-06-30 13F FASTENAL COM 311900104 3,460 0 0.00 204 9.68 0.0092
2023-05-16 2023-03-31 13F FASTENAL COM 311900104 3,460 0 0.00 187 14.11 0.0092
2023-02-10 2022-12-31 13F FASTENAL COM 311900104 3,460 0 0.00 164 2.52 0.0086
2022-11-15 2022-09-30 13F FASTENAL COM 311900104 3,460 0 0.00 159 -8.09 0.0088
2022-08-16 2022-06-30 13F FASTENAL COM 311900104 3,460 0 0.00 173 -16.02 0.0093
2022-05-16 2022-03-31 13F FASTENAL COM 311900104 3,460 0 0.00 206 -7.21 0.0089
2022-02-16 2021-12-31 13F FASTENAL COM 311900104 3,460 0 0.00 222 24.02 0.0082
2021-11-12 2021-09-30 13F FASTENAL COM 311900104 3,460 0 0.00 179 -0.56 0.0068
2021-08-17 2021-06-30 13F FASTENAL COM 311900104 3,460 0 0.00 180 3.45 0.0060
2021-05-14 2021-03-31 13F FASTENAL COM 311900104 3,460 0 0.00 174 2.96 0.0063
2021-02-17 2020-12-31 13F FASTENAL COM 311900104 3,460 0 0.00 169 8.33 0.0063
2020-11-16 2020-09-30 13F FASTENAL COM 311900104 3,460 0 0.00 156 5.41 0.0061
2020-08-14 2020-06-30 13F FASTENAL COM 311900104 3,460 0 0.00 148 37.04 0.0064
2020-05-13 2020-03-31 13F FASTENAL COM 311900104 3,460 0 0.00 108 -15.62 0.0064
2020-02-14 2019-12-31 13F FASTENAL COM 311900104 3,460 0 0.00 128 13.27 0.0051
2019-11-15 2019-09-30 13F FASTENAL COM 311900104 3,460 -64,460 -94.91 113 -94.90 0.0046
2019-08-13 2019-06-30 13F FASTENAL COM 311900104 67,920 31,710 87.57 2,214 -4.94 0.0849
2019-05-14 2019-03-31 13F FASTENAL COM 311900104 36,210 0 0.00 2,329 23.03 0.0877
2019-02-12 2018-12-31 13F FASTENAL COM 311900104 36,210 0 0.00 1,893 -9.90 0.0807
2018-11-14 2018-09-30 13F FASTENAL COM 311900104 36,210 0 0.00 2,101 20.54 0.0604
2018-08-15 2018-06-30 13F FASTENAL COM 311900104 36,210 0 0.00 1,743 -11.84 0.0537
2018-05-14 2018-03-31 13F FASTENAL COM 311900104 36,210 0 0.00 1,977 -0.15 0.0626
2018-02-15 2017-12-31 13F FASTENAL COM 311900104 36,210 0 0.00 1,980 20.00 0.0594
2017-11-15 2017-09-30 13F FASTENAL COM 311900104 36,210 0 0.00 1,650 4.70 0.0518
2017-08-15 2017-06-30 13F FASTENAL COM 311900104 36,210 -2,600 -6.70 1,576 -21.16 0.0515
2017-05-15 2017-03-31 13F FASTENAL COM 311900104 38,810 0 0.00 1,999 9.65 0.0626
2017-02-15 2016-12-31 13F FASTENAL COM 311900104 38,810 0 0.00 1,823 12.46 0.0581
2016-11-15 2016-09-30 13F FASTENAL COM 311900104 38,810 0 0.00 1,621 -5.92 0.0490
2016-08-10 2016-06-30 13F FASTENAL COM 311900104 38,810 0 0.00 1,723 -9.41 0.0550
2016-05-17 2016-03-31 13F FASTENAL COM 311900104 38,810 0 0.00 1,902 20.08 0.0594
2016-02-17 2015-12-31 13F FASTENAL COM 311900104 38,810 -5,320 -12.06 1,584 -1.98 0.0476
2015-11-17 2015-09-30 13F FASTENAL COM 311900104 44,130 0 0.00 1,616 -13.16 0.0520
2015-08-17 2015-06-30 13F FASTENAL COM 311900104 44,130 0 0.00 1,861 1.75 0.0497
2015-05-15 2015-03-31 13F FASTENAL COM 311900104 44,130 0 0.00 1,829 -12.86 0.0441
2015-02-10 2014-12-31 13F FASTENAL COM 311900104 44,130 -1,870 -4.07 2,099 -7.45 0.0541
2014-11-17 2014-09-30 13F FASTENAL COM 311900104 46,000 0 0.00 2,268 -0.40 0.0645
2014-08-15 2014-06-30 13F FASTENAL COM 311900104 46,000 0 0.00 2,277 0.40 0.0628
2014-05-20 2014-03-31 13F FASTENAL COM 311900104 46,000 0 0.00 2,268 3.80 0.0645
2014-02-20 2013-12-31 13F FASTENAL COM 311900104 46,000 1,870 4.24 2,185 10.30 0.0634
2014-11-21 2013-09-30 13F/A-1 FASTENAL COM 311900104 44,130 -9,270 -17.36 1,981 -18.98 0.0559
2013-11-20 2013-09-30 13F FASTENAL COM 311900104 53,400 2,684
2013-09-26 2013-06-30 13F FASTENAL COM 311900104 53,400 53,400 2,445 0.0811
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.