Dorman Products, Inc.
US ˙ NasdaqGS ˙ US2582781009

SecurityDORM / Dorman Products, Inc.
InstitutionSimplex Trading, Llc
Latest Disclosed Ownership67 shares
Latest Disclosed Value $ 6,992
Simplex Trading, Llc ownership in DORM / Dorman Products, Inc.

On May 14, 2026 - Simplex Trading, Llc filed a 13F-HR form disclosing ownership of 67 shares of Dorman Products, Inc. (US:DORM) valued at $6,992 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 2, 2023 disclosing 0 shares of Dorman Products, Inc.. The current value of the position is $8,358 USD.

Simplex Trading, Llc has a history of taking positions in derivatives of the underlying security (DORM) in the form of stock options. The firm currently holds call options representing 100 of underlying shares valued at $10,436 USD and put options representing 100 of underlying shares valued at $10,436 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

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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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

DORM / Dorman Products, Inc. Historical Put/Call Ratio
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)
2026-05-14 2026-03-31 13F DORMAN PRODS COM 258278100 67 67 7 0.0000
2023-02-02 2022-12-31 13F DORMAN PRODS COM 258278100 0 -262 -100.00 0 -100.00
2022-11-04 2022-09-30 13F DORMAN PRODS COM 258278100 262 -789 -75.07 21 -81.74 0.0000
2022-08-03 2022-06-30 13F DORMAN PRODS COM 258278100 1,051 -116 -9.94 115 4.55 0.0001
2022-05-02 2022-03-31 13F DORMAN PRODS COM 258278100 1,167 1,167 110 0.0001
2020-10-14 2020-09-30 13F DORMAN PRODUCTS COM 258278100 0 -1,300 -100.00 0 -100.00
2020-07-13 2020-06-30 13F DORMAN PRODUCTS COM 258278100 1,300 1,000 333.33 87 443.75 0.0001
2020-04-29 2020-03-31 13F DORMAN PRODUCTS COM 258278100 300 300 16 0.0000
2019-07-26 2019-06-30 13F DORMAN PRODUCTS COM 258278100 0 -492 -100.00 0 -100.00
2019-04-18 2019-03-31 13F DORMAN PRODUCTS COM 258278100 492 492 43 0.0001
2018-07-30 2018-06-30 13F DORMAN PRODUCTS COM 258278100 0 -86 -100.00 0 -100.00
2018-04-26 2018-03-31 13F DORMAN PRODUCTS COM 258278100 86 42 95.45 5 150.00 0.0002
2018-01-10 2017-12-31 13F DORMAN PRODUCTS COM 258278100 44 -309 -87.54 2 -92.00 0.0001
2017-10-25 2017-09-30 13F DORMAN PRODUCTS COM 258278100 353 353 25 0.0010
2016-01-20 2015-12-31 13F DORMAN PRODUCTS COM 258278100 0 -1,792 -100.00 0 -100.00
2015-10-08 2015-09-30 13F DORMAN PRODUCTS COM 258278100 1,792 -3,855 -68.27 91 -66.17 0.0067
2015-07-08 2015-06-30 13F DORMAN PRODUCTS COM 258278100 5,647 5,647 269 0.0225
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-14 2026-03-31 13F DORMAN PRODS CALL Call 100 -95.83 10 -96.61 n/a n/a n/a
2026-02-11 2025-12-31 13F DORMAN PRODS CALL Call 2,400 4.35 296 n/a n/a n/a
2025-11-12 2025-09-30 13F DORMAN PRODS CALL Call 2,300 27.78 0 n/a n/a n/a
2025-08-05 2025-06-30 13F DORMAN PRODS CALL Call 1,800 -66.04 0 n/a n/a n/a
2025-05-12 2025-03-31 13F DORMAN PRODS CALL Call 5,300 -29.33 1 n/a n/a n/a
2025-02-11 2024-12-31 13F DORMAN PRODS CALL Call 7,500 -30.56 1 -100.00 n/a n/a n/a
2024-11-08 2024-09-30 13F DORMAN PRODS CALL Call 10,800 92.86 1 n/a n/a n/a
2024-07-25 2024-06-30 13F DORMAN PRODS CALL Call 5,600 27.27 1 n/a n/a n/a
2024-04-25 2024-03-31 13F DORMAN PRODS CALL Call 4,400 -24.14 0 n/a n/a n/a
2024-02-02 2023-12-31 13F DORMAN PRODS CALL Call 5,800 38.10 0 n/a n/a n/a
2023-11-01 2023-09-30 13F DORMAN PRODS CALL Call 4,200 90.91 0 n/a n/a n/a
2023-08-04 2023-06-30 13F DORMAN PRODS CALL Call 2,200 0.00 0 n/a n/a n/a
2023-04-27 2023-03-31 13F DORMAN PRODS CALL Call 2,200 -18.52 0 n/a n/a n/a
2023-02-02 2022-12-31 13F DORMAN PRODS CALL Call 2,700 -44.90 0 -100.00 n/a n/a n/a
2022-11-04 2022-09-30 13F DORMAN PRODS CALL Call 4,900 44.12 402 7.77 n/a n/a n/a
2022-08-03 2022-06-30 13F DORMAN PRODS CALL Call 3,400 -12.82 373 0.81 n/a n/a n/a
2022-05-02 2022-03-31 13F DORMAN PRODS CALL Call 3,900 -22.00 370 -34.51 n/a n/a n/a
2022-02-23 2021-12-31 13F/A DORMAN PRODS CALL Call 5,000 72.41 565 85.25 n/a n/a n/a
2022-02-04 2021-12-31 13F DORMAN PRODS CALL Call 2,900 305 n/a n/a n/a
2021-10-28 2021-09-30 13F DORMAN PRODS CALL Call 2,900 0.00 305 1.67 n/a n/a n/a
2021-08-12 2021-06-30 13F DORMAN PRODS CALL Call 2,900 4,815.25 300 -50.41 n/a n/a n/a
2021-04-26 2021-03-31 13F DORMAN PRODS CALL Call 59 96.67 605 132.69 n/a n/a n/a
2021-02-02 2020-12-31 13F DORMAN PRODS CALL Call 30 36.36 260 31.31 n/a n/a n/a
2020-10-14 2020-09-30 13F DORMAN PRODUCTS CALL Call 22 144.44 198 230.00 n/a n/a n/a
2020-07-13 2020-06-30 13F DORMAN PRODUCTS CALL Call 9 -59.09 60 -50.41 n/a n/a n/a
2020-04-29 2020-03-31 13F DORMAN PRODUCTS CALL Call 22 -65.08 121 -74.63 n/a n/a n/a
2020-02-05 2019-12-31 13F DORMAN PRODUCTS CALL Call 63 18.87 477 13.30 n/a n/a n/a
2019-10-15 2019-09-30 13F DORMAN PRODUCTS CALL Call 53 5,200.00 421 5,162.50 n/a n/a n/a
2019-07-26 2019-06-30 13F DORMAN PRODUCTS CALL Call 1 0.00 8 0.00 n/a n/a n/a
2019-04-18 2019-03-31 13F DORMAN PRODUCTS CALL Call 1 0.00 8 0.00 n/a n/a n/a
2019-01-16 2018-12-31 13F DORMAN PRODUCTS CALL Call 0 -100.00 0 -100.00 n/a n/a n/a
2018-10-23 2018-09-30 13F DORMAN PRODUCTS CALL Call 48 4.35 369 17.52 n/a n/a n/a
2018-07-30 2018-06-30 13F DORMAN PRODUCTS CALL Call 46 -8.00 314 1,993.33 n/a n/a n/a
2018-04-26 2018-03-31 13F DORMAN PRODUCTS CALL Call 50 8.70 15 -95.22 n/a n/a n/a
2018-01-10 2017-12-31 13F DORMAN PRODUCTS CALL Call 0 -100.00 0 -100.00 n/a n/a n/a
2017-10-25 2017-09-30 13F DORMAN PRODUCTS CALL Call 14 0.00 2 100.00 n/a n/a n/a
2017-07-12 2017-06-30 13F DORMAN PRODUCTS CALL Call 14 0.00 1 -50.00 n/a n/a n/a
2017-01-11 2016-12-31 13F DORMAN PRODUCTS CALL Call 0 -100.00 0 n/a n/a n/a
2016-10-07 2016-09-30 13F DORMAN PRODUCTS CALL Call 9 -18.18 0 -100.00 n/a n/a n/a
2016-07-18 2016-06-30 13F DORMAN PRODUCTS CALL Call 11 1,000.00 3 n/a n/a n/a
2016-04-14 2016-03-31 13F DORMAN PRODUCTS CALL Call 1 -99.54 0 -100.00 n/a n/a n/a
2016-01-20 2015-12-31 13F DORMAN PRODUCTS CALL Call 217 768.00 74 825.00 n/a n/a n/a
2015-10-08 2015-09-30 13F DORMAN PRODUCTS CALL Call 25 56.25 8 100.00 n/a n/a n/a
2015-07-08 2015-06-30 13F DORMAN PRODUCTS CALL Call 16 100.00 4 300.00 n/a n/a n/a
2015-04-21 2015-03-31 13F DORMAN PRODUCTS CALL Call 8 60.00 1 -50.00 n/a n/a n/a
2015-03-04 2014-12-31 13F DORMAN PRODUCTS CALL Call 5 2 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-14 2026-03-31 13F DORMAN PRODS PUT Put 100 0.00 10 -16.67 n/a n/a n/a
2026-02-11 2025-12-31 13F DORMAN PRODS PUT Put 100 -88.89 12 n/a n/a n/a
2025-11-12 2025-09-30 13F DORMAN PRODS PUT Put 900 0 n/a n/a n/a
2025-08-05 2025-06-30 13F DORMAN PRODS PUT Put 0 -100.00 0 n/a n/a n/a
2025-05-12 2025-03-31 13F DORMAN PRODS PUT Put 300 -25.00 0 n/a n/a n/a
2025-02-11 2024-12-31 13F DORMAN PRODS PUT Put 400 0.00 0 n/a n/a n/a
2024-11-08 2024-09-30 13F DORMAN PRODS PUT Put 400 -88.89 0 n/a n/a n/a
2024-07-25 2024-06-30 13F DORMAN PRODS PUT Put 3,600 56.52 0 n/a n/a n/a
2024-04-25 2024-03-31 13F DORMAN PRODS PUT Put 2,300 15.00 0 n/a n/a n/a
2024-02-02 2023-12-31 13F DORMAN PRODS PUT Put 2,000 0 n/a n/a n/a
2023-02-02 2022-12-31 13F DORMAN PRODS PUT Put 0 -100.00 0 -100.00 n/a n/a n/a
2022-11-04 2022-09-30 13F DORMAN PRODS PUT Put 500 150.00 41 95.24 n/a n/a n/a
2022-08-03 2022-06-30 13F DORMAN PRODS PUT Put 200 21 n/a n/a n/a
2022-05-02 2022-03-31 13F DORMAN PRODS PUT Put 0 -100.00 0 -100.00 n/a n/a n/a
2022-02-23 2021-12-31 13F/A DORMAN PRODS PUT Put 100 -75.00 11 -73.81 n/a n/a n/a
2022-02-04 2021-12-31 13F DORMAN PRODS PUT Put 400 42 n/a n/a n/a
2021-10-28 2021-09-30 13F DORMAN PRODS PUT Put 400 0.00 42 2.44 n/a n/a n/a
2021-08-12 2021-06-30 13F DORMAN PRODS PUT Put 400 41 n/a n/a n/a
2021-04-26 2021-03-31 13F DORMAN PRODS PUT Put 0 -100.00 0 -100.00 n/a n/a n/a
2021-02-02 2020-12-31 13F DORMAN PRODS PUT Put 5 -96.60 43 -96.76 n/a n/a n/a
2020-10-14 2020-09-30 13F DORMAN PRODUCTS PUT Put 147 -20.11 1,328 7.62 n/a n/a n/a
2020-07-13 2020-06-30 13F DORMAN PRODUCTS PUT Put 184 348.78 1,234 446.02 n/a n/a n/a
2020-04-29 2020-03-31 13F DORMAN PRODUCTS PUT Put 41 173.33 226 100.00 n/a n/a n/a
2020-02-05 2019-12-31 13F DORMAN PRODUCTS PUT Put 15 -85.85 113 -86.60 n/a n/a n/a
2019-10-15 2019-09-30 13F DORMAN PRODUCTS PUT Put 106 5,200.00 843 4,858.82 n/a n/a n/a
2019-07-26 2019-06-30 13F DORMAN PRODUCTS PUT Put 2 -33.33 17 -34.62 n/a n/a n/a
2019-04-18 2019-03-31 13F DORMAN PRODUCTS PUT Put 3 -66.67 26 -67.90 n/a n/a n/a
2019-01-16 2018-12-31 13F DORMAN PRODUCTS PUT Put 9 -35.71 81 -24.30 n/a n/a n/a
2018-10-23 2018-09-30 13F DORMAN PRODUCTS PUT Put 14 27.27 107 42.67 n/a n/a n/a
2018-07-30 2018-06-30 13F DORMAN PRODUCTS PUT Put 11 -45.00 75 3,650.00 n/a n/a n/a
2018-04-26 2018-03-31 13F DORMAN PRODUCTS PUT Put 20 1,900.00 2 -97.33 n/a n/a n/a
2018-01-10 2017-12-31 13F DORMAN PRODUCTS PUT Put 1 -87.50 0 -100.00 n/a n/a n/a
2017-10-25 2017-09-30 13F DORMAN PRODUCTS PUT Put 8 -69.23 0 n/a n/a n/a
2017-07-12 2017-06-30 13F DORMAN PRODUCTS PUT Put 26 0 n/a n/a n/a
2016-01-20 2015-12-31 13F DORMAN PRODUCTS PUT Put 0 -100.00 0 -100.00 n/a n/a n/a
2015-10-08 2015-09-30 13F DORMAN PRODUCTS PUT Put 50 -3.85 4 -96.61 n/a n/a n/a
2015-07-08 2015-06-30 13F DORMAN PRODUCTS PUT Put 52 1,200.00 118 2,850.00 n/a n/a n/a
2015-04-21 2015-03-31 13F DORMAN PRODUCTS PUT Put 4 0 n/a n/a n/a
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.