Didn't even know conduit had a fire rating.
What is the application?
If it's for something like a fuel farm (pumping station) you probably could not do better than MI, all in all, it does not come out a lot more than Rigid if you're running a bunch of it.
Walls are fire rated, the individual components inside them are dependent upon them to provide the rating. Many applications you do want to insure a low smoke in case of fire.
