The Scale Armor is part of the Hexxit Gear mod. It is one of three sets of Hexxit Gear Armor. When fully equipped, the player gets infinite Strength, Resistance and Fire Resistance II potion effects, as well as the maximum 20 Armor Points, the equivalent to wearing full Diamond armor; it is also the most defensive armor, even from Rapiers.
This armor set gives Fire Resistance II, which have no difference from Fire Resistance I; it is unknown why the creator of this armor used Fire Resistance II instead of I.
Even though the amount of armor points is maxed out, making it look about as good as diamond (but less durability), it gives you Resistance I with the full set, therefore being better than diamond raw defense-wise (not taking into account the Fire Resistance and Strength).
The full set of armor is dubbed the best for melee battles, due to the Strength, Resistance and Fire Resistance buffs.