Atmus Filtration Technologies Set to Join S&P SmallCap 600

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.

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

Argus Apr 6 session

+0.68% close to close Open Argus

Details

News Market Reaction – SPGI

In the Apr 6 session, SPGI gained 0.68%, reflecting a mild positive market reaction.

Data tracked by StockTitan Argus on the day of publication.

Market Context

This announcement highlights a routine index maintenance action by S&P Dow Jones Indices, a division...

Analysis

This announcement highlights a routine index maintenance action by S&P Dow Jones Indices, a division of S&P Global (SPGI), with Atmus Filtration Technologies joining the S&P SmallCap 600 on April 9, 2026. It reflects S&P DJI’s ongoing role in managing widely followed benchmarks rather than a direct change to SPGI’s financials. In context, it complements recent strategic and product-focused updates, while investors may continue monitoring earnings, corporate actions, and sector trends for more material catalysts.

Key Figures

Index change effective date: April 9, 2026

Index change effective date

April 9, 2026

Effective date for ATMU joining S&P SmallCap 600 and AL deletion

Historical Context

5 past events · Latest: Mar 31

5 events

1. Mar 31

   Data product launch

   24h Move

   -0.0%

   Launch of private markets performance analytics datasets for private credit and real assets.

2. Mar 31

   Executive appointment

   24h Move

   +1.9%

   Appointment of Chief Technology & Transformation Officer to lead enterprise technology.

3. Mar 26

   Earnings schedule

   24h Move

   +1.0%

   Announcement of Q1 2026 earnings release date and conference call details.

4. Mar 25

   Investor day announcement

   24h Move

   -0.7%

   Mobility Global Investor Day ahead of planned separation into standalone public company.

5. Mar 20

   Market outlook report

   24h Move

   -0.4%

   Release of energy and AI demand outlook in Look Forward: Energy Futures report.

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

Key Terms

s&p smallcap 600, gics sector, s&p 500, dow jones industrial average

4 terms

s&p smallcap 600 financial

"April 9, 2026 | S&P SmallCap 600 | Addition | Atmus Filtration..."

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

"Ticker | GICS Sector -------------------------------------------------------------------------- April 9, 2026..."

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.

s&p 500 financial

"home to iconic financial market indicators, such as the S&P 500® and the Dow Jones..."

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

dow jones industrial average financial

"such as the S&P 500® and the Dow Jones Industrial Average®."

A stock market index that tracks the share prices of a small group of large, well-known companies to give a quick snapshot of how the broader market is doing. Think of it like a thermometer for the stock market: it uses a handful of heavyweight firms as representative samples to show whether investor sentiment is rising or falling, which helps investors gauge market trends and compare performance over time.

View in glossary

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

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/atmus-filtration-technologies-set-to-join-sp-smallcap-600-302733292.html

SOURCE S&P Dow Jones Indices

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

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.