He wants to put a what where??

Ok so my so is very very very into my ass my butt my butt hole doesn't matter. Last night he asked if he could eat it. I said sure. He hasn't yet, but today he asked if he could put a 12inch dildo in my ass. 😳 you guies. I'm not completely against it, but I am kind of concerned. Will it fit? He's put the same dildo in my vagina and it fit. But will it fit in my ass?? I've watched pornos and I see girls taking way bigger ones but I'm still kind of eh. Maybe he will get his rocks off by getting it half in. Have any of you done this before? I've done anal before I like it. 😪 I told him I was open to anything with him as long as we were the only two involved. Now I regret it.