Mirion Technologies Added to S&P 600 Information Technology Index

Mirion Technologies, a global provider of radiation detection and measurement solutions, has been added to the S&P 600 Information Technology index. The company's Medical segment offers products and services for radiation therapy, personal dosimetry, and nuclear medicine, while its Technologies segment serves defense, nuclear energy, laboratories, and research markets with reactor safety, radiological search, and measurement systems.

Mirion Technologies Inc. (NYSE: MIR) stock surged 7% in afterhours trading following news that the company will be added to the S&P SmallCap 600 index. The radiation detection and measurement solutions provider will replace GMS Inc. (NYSE: GMS) in the index, effective prior to the opening of trading on Tuesday, September 9, 2025 [1].

The index addition is a result of Home Depot Inc. (NYSE: HD) completing its acquisition of GMS today. The acquisition will see GMS become a subsidiary of Home Depot's specialty trade distribution subsidiary, SRS Distribution Inc. [2]. Mirion Technologies, an information technology company, will enter the S&P SmallCap 600 index, while GMS, a distributor of specialty building products, will exit the index [3].

The S&P SmallCap 600 index is a market-capitalization-weighted index of the 600 smallest companies in the S&P 1500 Composite Index. Index additions typically boost a company’s stock as funds tracking the benchmark must purchase shares to maintain accurate representation of the index. The S&P SmallCap 600 is widely followed by institutional investors and index funds [1].

Mirion Technologies operates in the Information Technology sector and offers a range of products and services for radiation therapy, personal dosimetry, nuclear medicine, defense, nuclear energy, laboratories, and research markets. The Medical segment includes solutions for calibrating and/or verifying imaging, treatment machine, patient treatment plan, and patient treatment accuracy, as well as monitoring radiation exposure for medical staff and products for nuclear medicine. The Technologies segment provides reactor safety and control systems, and radiological search, measurement, and analysis systems [2].

The index change will be implemented before markets open on September 9, giving investors and fund managers time to prepare for the adjustment to their portfolios. This highlights the dynamic nature of the financial markets and the impact of mergers and acquisitions on market indices. Investors should monitor the performance of both companies to understand the potential implications of this shift [3].

References:
[1] https://m.uk.investing.com/news/stock-market-news/mirion-technologies-stock-soars-after-joining-sp-smallcap-600-93CH-4251280?ampMode=1
[2] https://www.marketscreener.com/news/mirion-technologies-to-join-s-p-smallcap-600-ce7d59d9d88ffe25
[3] https://www.ainvest.com/news/mirion-technologies-replace-gms-smallcap-600-2509/