Reddit reviews ODM 4.5" Whitehead Dental Surgical Mouth Immobilizer Gag Stainless Steel

Called a "dental gag" and they're my fav

https://www.amazon.com/dp/B00IF48Q6I/ref=cm_sw_r_cp_awdb_t1_rrfxCbAHDTH4H

Edit: dental gag, Jennings gag or even spider gag.

https://www.kinkly.com/definition/14035/jennings-gag

Then get a mouth open gag. He can then put whatever he wants in there and it’s difficult for you to talk. If you’ve seen that new game where they have the mouth wide open gag they have to wear you’ll know what I’m talking about. You can buy a good one from a shop or the cheap plastic ones and make your own. Warning! If you tend to clamp down your jaw or grit your teeth during orgasm or other time DO NOT use the cheap plastic ones as they will break and you will get injured in your mouth.
Quick search returned this one on amazon.
https://www.amazon.com/dp/B00IF48Q6I/ref=sspa_mw_detail_2?psc=1
Many other types available
Play safe

Theyre dental equipment, so there's not really any "good" or "bad" ones out there. They're all pretty much the same. Just know that often, like in this listing, the whitehead is shown upsidedown.

ODM 4.5" Whitehead Dental Surgical Mouth Immobilizer Gag Stainless Steel https://www.amazon.com/dp/B00IF48Q6I/ref=cm_sw_r_cp_api_rRiczbRH3Q2NW