I have a Mossberg 500A.
Just be careful, measure your action slide tube first. This is designed to fit the 7 5/8 inch action slide tube (the part that the forend slips over). The product description unfortunately does not mention this.
As of 2006, Mossberg changed the action slide tube from 7 5/8 inches to 6 1/2 inches (for whatever reason), and the majority of forends on the market are for the older 7 5/8 inch one.
Hogue does make an extender nut, however I believe they label that as being for the Mossberg 835, so I did not try that.
So if you have the older 7 5/8 inch aciton slide tube, I'm sure this works great.
Pros: Probably works just fine, if it fits
Cons: Doesn't mention that it won't fit on newer Mossberg 500A's
This review was written in the old system and had content requirements that are different than reviews written today.