Masimo Corporation
US ˙ NasdaqGS ˙ US5747951003

SecurityMASI / Masimo Corporation
InstitutionSei Investments Co
Latest Disclosed Ownership0 shares
Latest Disclosed Value $ 0
Sei Investments Co ownership in MASI / Masimo Corporation

On May 13, 2026 - Sei Investments Co filed a 13F-HR form disclosing ownership of 0 shares of Masimo Corporation (US:MASI) valued at $0 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 7,715 shares of Masimo Corporation. This represents a change in shares of -100.00% during the quarter. The current value of the position is $0 USD.

Sei Investments Co has a history of taking positions in derivatives of the underlying security (MASI) in the form of stock options.

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.

MASI / Masimo Corporation 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)
2026-05-13 2026-03-31 13F MASIMO COM 574795100 0 -7,715 -100.00 0 -100.00
2026-02-13 2025-12-31 13F MASIMO COM 574795100 7,715 -13,940 -64.37 1,003 -68.61 0.0010
2025-11-13 2025-09-30 13F MASIMO COM 574795100 21,655 -8,851 -29.01 3,195 -37.73 0.0034
2025-08-14 2025-06-30 13F MASIMO COM 574795100 30,506 -18,859 -38.20 5,132 -37.61 0.0059
2025-05-14 2025-03-31 13F/A-1 MASIMO COM 574795100 49,365 22,764 85.58 8,224 87.04 0.0106
2025-05-13 2025-03-31 13F MASIMO COM 574795100 30,755 4,154 5,094 0.0055
2025-02-11 2024-12-31 13F MASIMO COM 574795100 26,601 -1,481 -5.27 4,397 17.44 0.0056
2024-11-12 2024-09-30 13F MASIMO COM 574795100 28,082 4,488 19.02 3,744 26.02 0.0049
2024-08-13 2024-06-30 13F MASIMO COM 574795100 23,594 -72,048 -75.33 2,971 -78.85 0.0042
2024-05-07 2024-03-31 13F MASIMO COM 574795100 95,642 -84,986 -47.05 14,045 -33.66 0.0206
2024-02-14 2023-12-31 13F MASIMO COM 574795100 180,628 -3,312 -1.80 21,171 31.28 0.0340
2023-11-14 2023-09-30 13F MASIMO COM 574795100 183,940 127,249 224.46 16,128 72.91 0.0290
2023-08-11 2023-06-30 13F MASIMO COM 574795100 56,691 14,686 34.96 9,328 20.33 0.0163
2023-05-12 2023-03-31 13F MASIMO COM 574795100 42,005 17,434 70.95 7,751 113.29 0.0144
2023-02-10 2022-12-31 13F MASIMO COM 574795100 24,571 -27,128 -52.47 3,635 -50.20 0.0081
2022-11-14 2022-09-30 13F MASIMO COM 574795100 51,699 5,245 11.29 7,297 19.62 0.0163
2022-08-15 2022-06-30 13F MASIMO COM 574795100 46,454 7,322 18.71 6,100 7.70 0.0132
2022-05-13 2022-03-31 13F MASIMO COM 574795100 39,132 -3,387 -7.97 5,664 -54.39 0.0114
2022-02-14 2021-12-31 13F MASIMO COM 574795100 42,519 3,437 8.79 12,419 17.45 0.0233
2021-11-12 2021-09-30 13F MASIMO COM 574795100 39,082 -2,434 -5.86 10,574 5.18 0.0222
2021-08-06 2021-06-30 13F MASIMO COM 574795100 41,516 -3,773 -8.33 10,053 -6.28 0.0223
2021-05-12 2021-03-31 13F MASIMO COM 574795100 45,289 5,007 12.43 10,727 -1.80 0.0270
2021-02-08 2020-12-31 13F MASIMO COM 574795100 40,282 -2,800 -6.50 10,924 7.74 0.0282
2020-12-04 2020-09-30 13F/A-1 MASIMO COM 574795100 43,082 10,127 30.73 10,139 34.43 0.0294
2020-11-06 2020-09-30 13F MASIMO COM 574795100 43,564 10,609 10,253 24,686.9444
2020-08-17 2020-06-30 13F/A-1 MASIMO COM 574795100 32,955 4,311 15.05 7,542 48.46 0.0234
2020-08-11 2020-06-30 13F MASIMO COM 574795100 39,760 11,116 7,152 19,400.1807
2020-05-14 2020-03-31 13F MASIMO COM 574795100 28,644 -6,954 -19.53 5,080 -9.77 0.0187
2020-02-06 2019-12-31 13F MASIMO COM 574795100 35,598 -18,555 -34.26 5,630 -29.79 0.0168
2019-11-12 2019-09-30 13F MASIMO COM 574795100 54,153 -11,119 -17.03 8,019 -17.32 0.0205
2019-08-14 2019-06-30 13F MASIMO COM 574795100 65,272 -1,346 -2.02 9,699 5.25 0.0317
2019-05-15 2019-03-31 13F MASIMO COM 574795100 66,618 14,236 27.18 9,215 49.42 0.0309
2019-02-13 2018-12-31 13F MASIMO COM 574795100 52,382 18,858 56.25 6,167 47.85 0.0220
2018-11-08 2018-09-30 13F MASIMO COM 574795100 33,524 -14,608 -30.35 4,171 -11.24 0.0151
2018-08-03 2018-06-30 13F MASIMO COM 574795100 48,132 4,418 10.11 4,699 22.21 0.0160
2018-05-11 2018-03-31 13F MASIMO COM 574795100 43,714 15,898 57.15 3,845 62.99 0.0147
2018-02-08 2017-12-31 13F MASIMO COM 574795100 27,816 -2,605 -8.56 2,359 -10.41 0.0082
2017-11-06 2017-09-30 13F MASIMO COM 574795100 30,421 -24,931 -45.04 2,633 -47.83 0.0094
2017-07-31 2017-06-30 13F MASIMO COM 574795100 55,352 -5,192 -8.58 5,047 -10.63 0.0201
2017-05-05 2017-03-31 13F MASIMO COM 574795100 60,544 1,932 3.30 5,647 42.93 0.0247
2017-02-02 2016-12-31 13F MASIMO COM 574795100 58,612 6,827 13.18 3,951 28.28 0.0191
2016-11-04 2016-09-30 13F MASIMO COM 574795100 51,785 1,365 2.71 3,080 16.31 0.0156
2016-08-11 2016-06-30 13F MASIMO COM 574795100 50,420 -4,335 -7.92 2,648 15.58 0.0159
2016-05-10 2016-03-31 13F/A-1 MASIMO COM 574795100 54,755 43,775 398.68 2,291 402.41 0.0143
2016-02-03 2015-12-31 13F MASIMO COM 574795100 10,980 -3,101 -22.02 456 -16.02 0.0028
2015-11-02 2015-09-30 13F/A-1 MASIMO COM 574795100 14,081 7,770 123.12 543 122.54 0.0050
2015-10-30 2015-09-30 13F MASIMO COM 574795100 14,081 544
2015-08-07 2015-06-30 13F/A-1 MASIMO COM 574795100 6,311 6,209 6,087.25 244 8,033.33 0.0022
2015-08-04 2015-06-30 13F MASIMO COM 574795100 6,311 6,209 244 0.0022
2015-05-14 2015-03-31 13F/A-1 MASIMO COM 574795100 102 93 1,033.33 3 0.0000
2015-05-01 2015-03-31 13F MARRONE BIO INNOVATIONS PUT 574795100 102 102 3 0.0000
2015-02-10 2014-12-31 13F MASIMO COM 574795100 9 9 0 0.0000
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
(%)
2015-05-01 2015-03-31 13F MARRONE BIO INNOVATIONS PUT 102 3 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.