Is it normal to fist ass

I use toys too

Try butt plugs and toys instead

The fact you can fit one in your ass is what I find astonishing.

Not normal for me because I can't reach. My joints aren't that flexible (or my arms are too short). If I could, I don't think I would, though. Although if someone else wanted to, I might let them. I'd be looking closely at the size of their hands first, though.