This models footprint is set for the Sig Sauer's ROMEO1PRO and Deltapoint Pro optics systems. Any other optic choice would require an adapter plate.

James, From the factory this pistol is set up to take the SIG Romeo1 Pro optic, which has the same footprint as the Leupold DeltaPoint Pro. Aftermarket companies make adapter plates for other red dots like the Aimpoint Acro. Have a great day!

James, the optics-ready XSeries slide is compatible with Sig Sauer's ROMEO1PRO and Deltapoint Pro optics systems. You can install a Trijicon RMR but you would have to purchase an adapter plate. Hope this helps.

James, Delta Point Pro, RMR and Romeo 1 Pro. Adapter Plat options listed here : https://reddotshooters.com/best-red-dot-for-sig-p320/#:~:text=The%20best%20red%20dot%20for%20the%20Sig%20P320%20is%20the,use%20of%20an%20adapter%20plate%E2%80%A6