Sirius XM Holdings Set to Join S&P MidCap 400

Sirius XM Holdings (NASD: SIRI) will join the S&P MidCap 400, replacing Masimo (NASD: MASI), effective before the market opens on June 11, 2026.

Rhea-AI Summary

Sirius XM Holdings (NASD: SIRI) will join the S&P MidCap 400, replacing Masimo (NASD: MASI), effective before the market opens on June 11, 2026. Danaher (NYSE: DHR), an S&P 500 and 100 constituent, is acquiring Masimo, with the deal expected to close after final conditions.

On June 11, 2026, Sirius XM will be added to the index as a Communication Services company, while Masimo will be removed from the index’s Health Care sector.

Positive

• Sirius XM added to S&P MidCap 400 on June 11, 2026
• Danaher to acquire Masimo, transaction pending final conditions

Negative

• Masimo to be deleted from S&P MidCap 400 on June 11, 2026

Argus Jun 9 session

+0.01% close to close Open Argus

Details

News Market Reaction – MASI

In the Jun 9 session, MASI gained 0.01%, reflecting a mild positive market reaction.

Data tracked by StockTitan Argus on the day of publication.

Market Context

This announcement links Masimo’s pending cash acquisition by Danaher to its removal from the S&P Mid...

Analysis

This announcement links Masimo’s pending cash acquisition by Danaher to its removal from the S&P MidCap 400 on June 11, 2026, with Sirius XM taking its place. Historically, the key price impact occurred when the $180.00-per-share deal was first announced, with later approvals and filings producing smaller moves. Investors tracking Masimo have focused on closing conditions, regulatory approvals, and the timeline to delisting as the main remaining milestones.

Key Figures

Index addition date: June 11, 2026

Index addition date

June 11, 2026

Effective date for S&P MidCap 400 changes involving MASI and SIRI

Historical Context

5 past events · Latest: May 04

5 events

1. May 04

   Merger approval

   24h Move

   -0.1%

   Shareholders approved the $180 cash acquisition by Danaher at a special meeting.

2. Apr 28

   Clinical study data

   24h Move

   -0.1%

   NeoPODS study showed accurate pulse oximetry performance across skin tones in newborns.

3. Feb 17

   Acquisition announcement

   24h Move

   +34.2%

   Danaher agreed to acquire Masimo for $180 per share in a $9.9B cash deal.

4. Feb 17

   Deal details

   24h Move

   +34.2%

   Danaher outlined valuation, synergy expectations, and accretion from the Masimo acquisition.

5. Feb 12

   Earnings date notice

   24h Move

   -1.5%

   Company scheduled Q4 and full-year 2025 results release and conference call.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

s&p midcap 400, s&p 500, s&p 100, gics sector

4 terms

s&p midcap 400 financial

"Sirius XM Holdings Inc. (NASD: SIRI) will replace Masimo Corp. (NASD: MASI) in the S&P MidCap 400 effective prior..."

The S&P MidCap 400 is a group of 400 companies that are smaller than the big, well-known corporations but larger than tiny startups. It helps investors see how medium-sized companies are performing in the stock market, acting like a barometer for this middle-sized group of businesses.

s&p 500 financial

"S&P 500 & 100 constituent Danaher Corp. (NYSE: DHR) is acquiring Masimo..."

The S&P 500 is a broad stock market index that tracks the performance of 500 large U.S. companies, weighted so bigger firms have a larger impact. Investors use it like a thermometer or benchmark to judge how the overall U.S. stock market or a portfolio is doing; movements in the index influence investor sentiment, fund performance, and many passive investment products that aim to match its returns.

View in glossary

s&p 100 financial

"S&P 500 & 100 constituent Danaher Corp. (NYSE: DHR) is acquiring Masimo..."

The S&P 100 is a stock market index that tracks the shares of 100 large, well‑established U.S. companies selected for size and ease of trading; think of it as a basket representing the biggest, most widely traded American firms. Investors use it as a quick read on how large‑cap, blue‑chip stocks are performing and as a benchmark for funds and derivatives; like checking the temperature of the largest businesses, movements in the index can influence portfolio choices and risk management.

gics sector financial

"Effective Date | Index Name | Action | Company Name | Ticker | GICS Sector"

GICS sector is one of the major industry groupings from the Global Industry Classification Standard, a system that sorts companies into consistent categories (like Technology or Health Care) based on the primary business they do. Investors use these sectors like folders in a filing cabinet to compare companies, build diversified portfolios, and track how whole parts of the market are performing rather than focusing on single stocks.

AI-generated analysis. How Rhea-AI works. Not financial advice.

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

NEW YORK, June 8, 2026 /PRNewswire/ -- Sirius XM Holdings Inc. (NASD: SIRI) will replace Masimo Corp. (NASD: MASI) in the S&P MidCap 400 effective prior to the opening of trading on Thursday, June 11. S&P 500 & 100 constituent Danaher Corp. (NYSE: DHR) is acquiring Masimo in a deal expected to be completed soon pending final conditions.

Following is a summary of the changes that will take place prior to the open of trading on the effective date:

Effective Date	Index Name	Action		Company Name	Ticker	GICS Sector
June 11, 2026	S&P MidCap 400		Addition	Sirius XM Holdings	SIRI	Communication Services
June 11, 2026	S&P MidCap 400		Deletion	Masimo	MASI	Health Care

ABOUT S&P DOW JONES INDICES

S&P Dow Jones Indices is the largest global resource for essential index-based concepts, data and research, and home to iconic financial market indicators, such as the S&P 500® and the Dow Jones Industrial Average®. More assets are invested in products based on our indices than products based on indices from any other provider in the world. Since Charles Dow invented the first index in 1884, S&P DJI has been innovating and developing indices across the spectrum of asset classes helping to define the way investors measure and trade the markets.

S&P Dow Jones Indices is a division of S&P Global (NYSE: SPGI), which provides essential intelligence for individuals, companies, and governments to make decisions with confidence. For more information, visit www.spglobal.com/spdji/en/.

FOR MORE INFORMATION:

S&P Dow Jones Indices
index_services@spglobal.com

Media Inquiries
spdji.comms@spglobal.com

View original content:https://www.prnewswire.com/news-releases/sirius-xm-holdings-set-to-join-sp-midcap-400-302794483.html

SOURCE S&P Dow Jones Indices

FAQ

What change is S&P making to the S&P MidCap 400 on June 11, 2026?

S&P Dow Jones Indices will add Sirius XM Holdings and remove Masimo from the S&P MidCap 400 on June 11, 2026. According to S&P Dow Jones Indices, the reshuffle becomes effective before trading opens on that Thursday for index tracking and benchmark purposes.

When will Sirius XM Holdings (NASD: SIRI) be added to the S&P MidCap 400 index?

Sirius XM Holdings will be added to the S&P MidCap 400 before the market opens on Thursday, June 11, 2026. According to S&P Dow Jones Indices, Sirius XM will enter the index’s Communication Services sector on that effective date.

Why is Masimo (NASD: MASI) being removed from the S&P MidCap 400 in June 2026?

Masimo is being removed from the S&P MidCap 400 because Danaher is acquiring the company, pending final conditions. According to S&P Dow Jones Indices, Masimo’s deletion from the index will take effect before trading begins on June 11, 2026.

How is Danaher (NYSE: DHR) involved in the S&P MidCap 400 changes announced for June 2026?

Danaher is acquiring Masimo, which triggers Masimo’s removal from the S&P MidCap 400 index. According to S&P Dow Jones Indices, Danaher is an S&P 500 and S&P 100 member, and the Masimo transaction is expected to close after remaining conditions are satisfied.

What sector classifications apply to Sirius XM and Masimo in the June 11, 2026 S&P MidCap 400 update?

Sirius XM will join the S&P MidCap 400 as a Communication Services company, while Masimo exits from the Health Care sector. According to S&P Dow Jones Indices, both changes occur before the opening of trading on June 11, 2026.