Armor Material Mastery (Armor Mastery, Combat)Source Armor Master's Handbook pg. 16
You bring the most out of your armor’s special material.
Prerequisites: Armor Material Expertise, base attack bonus +11 or fighter level 8th, armor training class feature.
Benefit: You can use the ability granted by Armor Material Expertise two additional times per day.Source Armor Master's Handbook pg. 20 (Amazon)
You can spend 5 stamina points to use an armor material ability without it counting against your daily limit. (See page 16.)