Grant, chokes are changeable, but it only comes with 1 cylinder bore choke tube.

this is the Cobra III Tactical and it comes with 1 cyl beretta mobli choke tube tristararms.com/series/cobra-iii-tactical/

I just watched 3 YouTube videos on this shotgun, never a mention of the chokes/system. As James said you can try to contact Tristar, but honestly with these smaller companies it can be difficult to get a reply, they don't have the same customer service as the bigger companies, I emailed Century arms on Friday with a question and still haven't heard back, Glock, Ruger, SW, and all the other big companies usually reply within a day.

Grant, the Marine model uses Beretta/Benelli Chokes. I assume the same but would contact TriStar Customer Service to confirm : tristararms.com/faqs/