Sirius XM Holdings Set to Join S&P MidCap 400

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.

AI-generated analysis. Not financial advice.

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

Key Figures

Index addition date: June 11, 2026

1 metrics

Index addition date June 11, 2026 Effective date for S&P MidCap 400 changes involving MASI and SIRI

Market Reality Check

Price: $178.82 Vol: Volume 1,266,141 vs 20-da...

normal vol

$178.82 Last Close

Volume Volume 1,266,141 vs 20-day average 888,889, indicating elevated trading activity ahead of index removal. normal

Technical Price at 179.94 is above 200-day MA of 155.72, reflecting a stabilized, deal-anchored level.

Peers on Argus

MASI gained 0.63% while key medical device peers (GMED -1.74%, BIO -1.42%, IRTC ...

MASI gained 0.63% while key medical device peers (GMED -1.74%, BIO -1.42%, IRTC -0.91%, GKOS -1.79%, BRKR -2.34%) traded lower, pointing to stock-specific dynamics tied to its pending acquisition and index deletion.

Historical Context

5 past events · Latest: May 04 (Positive)

Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
May 04	Merger approval	Positive	-0.1%	Shareholders approved the $180 cash acquisition by Danaher at a special meeting.
Apr 28	Clinical study data	Positive	-0.1%	NeoPODS study showed accurate pulse oximetry performance across skin tones in newborns.
Feb 17	Acquisition announcement	Positive	+34.2%	Danaher agreed to acquire Masimo for $180 per share in a $9.9B cash deal.
Feb 17	Deal details	Positive	+34.2%	Danaher outlined valuation, synergy expectations, and accretion from the Masimo acquisition.
Feb 12	Earnings date notice	Neutral	-1.5%	Company scheduled Q4 and full-year 2025 results release and conference call.

Pattern Detected

Recent major acquisition headlines produced strong positive moves, while follow-up approvals and technical/clinical updates saw flat-to-slightly-negative reactions.

Recent Company History

Over the past few months, Masimo’s trajectory has been dominated by its sale to Danaher. On Feb 17, 2026, news of the $180.00-per-share, roughly $9.9 billion acquisition triggered a sharp positive move of about 34%. Subsequent events, including shareholder approval on May 4, 2026 and strong Q1 results, saw only modest price shifts around the agreed cash consideration. Today’s index deletion ties directly to this process of transitioning Masimo into Danaher’s ownership and eventual delisting.

Market Pulse Summary

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 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.

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. Not financial advice.

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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

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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.