Natural AC question

[Slacker2010]

For the Eidolon, Most of the base forms have Natural Armor +2. There is a "Improved Natural Armor" evolution that gives +2 Natural Armor each time you take it. These effects stack or you couldn't take it more than once. Would giving your Eidolon an Amulet of Natural Armor stack as well? They are all the same bonus and the the first two stack. I was curious if the Magic Item bonus stacked and if it doesn't, then why not?

[Rathendar]

Slacker2010 wrote:

For the Eidolon, Most of the base forms have Natural Armor +2. There is a "Improved Natural Armor" evolution that gives +2 Natural Armor each time you take it. These effects stack or you couldn't take it more than once. Would giving your Eidolon an Amulet of Natural Armor stack as well? They are all the same bonus and the the first two stack. I was curious if the Magic Item bonus stacked and if it doesn't, then why not?

RAW, yes they do. The amulet is an enhancement bonus to the natural armor value, much like magic armor is an enhancement bonus to the Armor value.

[spook54321]

simply put there is your
-base natural armor bonus
-natural armor enhancement bonus

The evolutions modify the base natural armor bonus and are not an enhancement bonus.

The amulet is a natural armor enhancement bonus. It can stack with the base natural armor bonus without problems, but cannot stack with other enhancement bonuses, such as from the spell barkskin. The highest bonus applies in this event.