Atmus Filtration Technologies Set to Join S&P SmallCap 600

Rhea-AI Summary

Atmus Filtration Technologies (NYSE:ATMU) will be added to the S&P SmallCap 600 and will replace Air Lease (NYSE:AL) effective prior to the open of trading on April 9, 2026.

S&P Dow Jones Indices said the table of index changes lists ATMU as an addition and AL as a deletion on that effective date; a Sumitomo Corporation & consortium acquisition of Air Lease is expected to close pending final conditions.

Positive

• ATMU added to S&P SmallCap 600 effective April 9, 2026
• AL removed from S&P SmallCap 600 effective April 9, 2026
• Acquisition pending for Air Lease by Sumitomo & consortium, per announcement

Negative

• Index exclusion for AL effective April 9, 2026
• AL acquisition remains subject to final closing conditions

News Market Reaction – ATMU

+4.37%

2 alerts

+4.37% News Effect

+$197M Valuation Impact

$4.71B Market Cap

0.0x Rel. Volume

On the day this news was published, ATMU gained 4.37%, reflecting a moderate positive market reaction. Our momentum scanner triggered 2 alerts that day, indicating moderate trading interest and price volatility. This price movement added approximately $197M to the company's valuation, bringing the market cap to $4.71B at that time.

Data tracked by StockTitan Argus on the day of publication.

Market Context

This announcement adds Atmus to the S&P SmallCap 600 effective April 9, 2026, replacing Air Lease Co...

Analysis

This announcement adds Atmus to the S&P SmallCap 600 effective April 9, 2026, replacing Air Lease Corp. It follows a series of constructive updates, including FY 2025 sales of $1.764 billion, net income of $207 million, the Koch Filter acquisition, and a quarterly dividend of $0.055 per share. Investors may watch how index inclusion interacts with this operational momentum, as well as ongoing governance and compensation structures detailed in recent proxy and Form 4 filings.

Key Figures

Index effective date: April 9, 2026 Index name: S&P SmallCap 600

2 metrics

Index effective date April 9, 2026 Date ATMU joins S&P SmallCap 600

Index name S&P SmallCap 600 ATMU added, AL removed

Historical Context

5 past events · Latest: Mar 31 (Positive)

Pattern 5 events

Date	Event	Sentiment	24h Move	Catalyst
Mar 31	Lab expansion	Positive	+3.6%	Opened expanded certified testing lab in Quimper to boost capacity.
Feb 13	Earnings & guidance	Positive	+3.2%	Reported FY 2025 results, Koch Filter acquisition, and 2026 guidance.
Feb 09	Dividend declaration	Positive	+1.0%	Declared quarterly cash dividend of $0.055 per common share.
Feb 06	Board appointment	Positive	+1.5%	Added experienced manufacturing executive Heath Sharp to Board.
Jan 29	Earnings date set	Neutral	+2.1%	Announced timing and webcast details for Q4 and FY 2025 results.

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

Pattern Detected

Recent company-specific news, including earnings, dividends, and operational updates, has generally coincided with positive next-day returns, suggesting investors have rewarded Atmus’s execution milestones.

Recent Company History

Over the past few months, Atmus reported several constructive developments. On Feb 13, 2026, it posted FY 2025 sales of $1,764M, net income of $207M, and Adjusted EBITDA of $354M, alongside 2026 revenue and EPS guidance and completion of the Koch Filter acquisition. A quarterly dividend of $0.055 per share was declared on Feb 9, 2026. Operational and governance steps followed, including a new director appointment and an expanded Quimper testing lab. Those events all saw positive single-day price reactions, providing a constructive backdrop to today’s index inclusion news.

Key Terms

s&p smallcap 600, gics sector

2 terms

s&p smallcap 600 financial

"Atmus Filtration Technologies Inc. (NYSE: ATMU) will replace Air Lease Corp. (NYSE: AL) in the S&P SmallCap 600 effective prior to the opening of trading on Thursday, April 9."

A stock market index made up of 600 small-cap U.S. companies chosen to represent the performance of smaller publicly traded firms. It matters to investors because it acts like a temperature gauge for the small-company segment of the market, serving as a benchmark for fund managers, a basis for index funds and ETFs, and a way to compare returns and risk when building a diversified portfolio.

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.

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NEW YORK, April 2, 2026 /PRNewswire/ -- Atmus Filtration Technologies Inc. (NYSE: ATMU) will replace Air Lease Corp. (NYSE: AL) in the S&P SmallCap 600 effective prior to the opening of trading on Thursday, April 9. Sumitomo Corporation & Consortium are acquiring Air Lease Corp in a deal expected to be completed soon, pending final closing 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
April 9, 2026	S&P SmallCap 600	Addition		Atmus Filtration Technologies	ATMU	Industrials
April 9, 2026	S&P SmallCap 600	Deletion		Air Lease	AL	Industrials

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View original content:https://www.prnewswire.com/news-releases/atmus-filtration-technologies-set-to-join-sp-smallcap-600-302733292.html

SOURCE S&P Dow Jones Indices

FAQ

When will Atmus Filtration Technologies (ATMU) join the S&P SmallCap 600?

ATMU will join the S&P SmallCap 600 effective prior to the open on April 9, 2026. According to S&P Dow Jones Indices, the change lists ATMU as an addition and will take effect before trading begins that day.

Why is Air Lease (AL) being removed from the S&P SmallCap 600 on April 9, 2026?

Air Lease is being deleted from the S&P SmallCap 600 effective April 9, 2026. According to S&P Dow Jones Indices, the deletion coincides with a pending acquisition by Sumitomo Corporation and a consortium.

Does the press release say the Sumitomo acquisition of Air Lease (AL) is complete?

No, the acquisition is not complete; it is expected to close pending final conditions. According to S&P Dow Jones Indices, the deal is anticipated to be completed soon but remains subject to closing requirements.

What is the effective date for both the ATMU addition and AL deletion from S&P SmallCap 600?

Both the addition of ATMU and deletion of AL are effective prior to the open of trading on April 9, 2026. According to S&P Dow Jones Indices, the table of index changes lists that effective date for both actions.

Which sectors are listed for Atmus (ATMU) and Air Lease (AL) in the index change?

Both companies are listed under the Industrials GICS sector in the index update. According to S&P Dow Jones Indices, the table shows ATMU and AL assigned to Industrials for the April 9, 2026 changes.