I have not used these personally for my bunnies but I know that many other have and they are fine to use for bunnies.

I might have to switch Griffin to a covered pan as he tends to pee over the edge of the litterbox- he is bigger and has longer legs than my other bunnies so that might be why he is “missing” sometimes.

Jersey used one for a while.  Some bunnies might be deterred by the flap or having only one exit/entry point.  I use just the base now for both buns. It’s good as it’s low at front and high backed.  I”ve also cut plastic storage box down to same shape as 2nd box. 

This is from BB litter training tips – Bailey in a lipped pan. That might be worth a look too.  Or high sided pans.

One of my bunny also does this so I got him a larger litter box with high back. And it did the trick.

I just switched Sammy to the same thing. She now has a high-backed rectangular (almost square) pan.