Armor

Magic and psionic armor protects the wearer better than armor without any enhancement. Magic and psionic armor provide enhancement bonuses that stack with the equipment bonuses provided by the armor. Further, all armor penalties for magic and psionic armor are reduced by 1.
In addition to an enhancement bonus, armor may have special qualities. Armor with special qualities must have at least a +1 enhancement bonus.
Magic and psionic armor resizes itself to fit the wearer.
Magic or psionic armor confers its enhancement bonus to Defense for as long as it's worn. If armor has a special quality that the wearer needs to activate, then the wearer needs to utter a command word (an attack action).
Purchase DC: To calculate the purchase DC for armor with an enhancement bonus but no special qualities, use the following table.
Enhancement Bonus
Purchase DC Modifier
+1
+8
+2
+13
+3
+18
Armor with special qualities has an additional purchase DC modifier, as noted under each item entry.
Examples of armor with special qualities include the following.