Spell penetration

Spell Penetration check

 * See Spell resistance

Spell Penetration feats

 * Spell Penetration feat gives +2 to die roll
 * Greater Spell Penetration feat gives another +2 to die roll

Spell Penetration enhancements

 * Improved Spell Penetration class enhancements gives +1 to +3 to die roll
 * Elven Arcanum gives up to +4

Spell Penetration item enchantment
The Spell Penetration item enchantment comes in 3 different flavors:
 * Minor Spell Penetration gives a +1 bonus
 * Spell Penetration (with no additional qualifier) gives a +2 bonus
 * Greater Spell Penetration gives a +3 bonus

In addition, an item's Spell Penetration bonus applies only for spells up to a given level, for instance a Spell Penetration III Dagger will give a +2 bonus for spells of the levels 1, 2, and 3.