This is the info I have:
The Stoeger STR-9 9mm 4.17" Optic Ready Slide uses a Shield RMSc footprint for mounting red dot sights. This means it's compatible with optics that share the RMSc footprint, such as the Holosun 407K/507K, Sig Sauer RomeoZero, and Swampfox Sentinel.
The STR-9 Optic Ready models come with multiple adapter plates to accommodate various red dot sights, including those with the RMSc footprint. The included plates allow for easy installation of different optic models, and a cover plate is provided for when an optic isn't mounted.

Hi Tristan and welcome. The Stoeger STR9/STR9-C optics ready models feature a proprietary slide cut and come with different steel optics plates. This guide will help you with the selection of the best Red/Green Dot for your needs. https://freedomgorilla.com/blogs/news/best-stoeger-str-9-holosun-optics-red-green-dot-sights?collection=&view=sl-133883E8#footprint -------------------------- Cheers, stay safe and enjoy!