SRD:Spell Resistance (Armor Enhancement)

Spell Resistance: This property grants the armor’s wearer spell resistance while the armor is worn. The spell resistance can be 13, 15, 17, or 19, depending on the armor.

Strong abjuration; CL 15th; Craft Magic Arms and Armor, spell resistance; Price +2 bonus (SR 13), +3 bonus (SR 15), +4 bonus (SR 17), or +5 bonus (SR 19).