That is correct, here is the description in the advertisement.
Details
Heat shield for your 500 or 590 plain barrel shotgun. Parkerized finish.
(Not compatible with ghost ring sight barrels or A1 heavy-walled barrels).
I have a tri-rail on my A1 and I'm still up in the air as to wither I it. I think at this point, I would have preferred that the bottom rail was only half the length like the two side rails.