Index change event
S&P SmallCap 600 Additions & Index Changes: ATMU – 2nd April 2026
On 2 April 2026, S&P Dow Jones Indices announced 2 index changes affecting 2 companies in the S&P SmallCap 600. Atmus Filtration Technologies replaced Air Lease in the S&P SmallCap 600.
Announced
2026-04-02
Effective
April 8, 2026 at 5:00:00 PM
Indexes Affected
S&P SmallCap 600
2
Index Changes in Total
1
Additions
1
Deletions
0
Companies that changed index
What happened to the prices
By the next day's close, Atmus Filtration Technologies, the only addition with price data, had peaked at +1.85%, against +0.06% for Air Lease, the only deletion with price data. The moves are measured from the first extended-hours price after the announcement, except for 1 name with no recorded trade after 17:15 ET, measured from the 16:00 ET close.
With one addition and one deletion priced, there is no group to stand out from: Atmus Filtration Technologies opened the next day at +0.25% and Air Lease at +0.05%, both from the post-announcement price.
In Short
2 index changes: 1 addition and 1 deletion.
No company moved from one S&P index to another in this announcement.
Largest peak move: Atmus Filtration Technologies, +1.85% by the next day's close.
The changes, index by index
An empty cell means the company was not in the S&P family before, or left it.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
S&P SmallCap 600 Additions: Atmus Filtration Technologies (ATMU)
1 company joined the S&P SmallCap 600 and 1 left, effective 9 April 2026. Atmus Filtration Technologies is new to the S&P family and Air Lease left the S&P family. Atmus Filtration Technologies peaked at +1.85% by the next day's close.
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Atmus Filtration Technologies | ATMU | S&P SmallCap 600 | 04/09/2026 |
Company | Ticker | Source Index | Final Index | Effective Date |
|---|---|---|---|---|
Price reaction
The close price is the last price before the announcement. Percentages are measured from the open price after the announcement, or from the close for a company with no price after it.
S&P 500 Additions Changes
Company | Ticker | Source Index | Final Index | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Change by Next Day Open | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|---|---|---|
S&P MidCap 400 Additions Changes
Company | Ticker | Source Index | Final Index | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Change by Next Day Open | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|---|---|---|
S&P SmallCap 600 Additions Changes
Not a Investment Advice
Company | Ticker | Source Index | Final Index | Close Price | Open Price at Announcement | % Change +5 min | % Change +30 min | % Change at 20:00 Hrs | % Change by Next Day Open | % Highest Change by Next Day Close |
|---|---|---|---|---|---|---|---|---|---|---|
Atmus Filtration Technologies | ATMU | S&P SmallCap 600 | 57.62 | 59.38 | -0.54% | -0.54% | +1.04% | +0.25% | +1.85% |
Not a Investment Advice
This page is research about past price behaviour. It is not a recommendation to buy or sell.