SRD
Mage Armor
Conjuration \ creation \ Force
Casting time: 1 standard action
Range: Touch
Duration: 1 hour/level (D)
Effect: Will negates (harmless)
Targets: creature touched
Bloodline: Draconic
Description
An invisible but tangible field of force surrounds the subject of a mage armor spell, providing a +4 armor bonus to AC.
Unlike mundane armor, mage armor entails no armor check penalty, arcane spell failure chance, or speed reduction. Since mage armor is made of force, incorporeal creatures can’t bypass it the way they do normal armor.