The rank of a item, determines its quality.
C-Rank items are the least valuable and most common.
B-Rank items are uncommon.
A-Rank is the third highest rarity of materials and equipment. A-Rank items are a soft red. When an A-Rank equipment is acquired during a quest, it is featured in a chest with golden metal and soft red wood.
S-Rank items are extremely rare and very valuable.
SS-Rank are the most rare and powerful of all of the materials and equipment. SS-Rank materials are only acquired in the highest levels of quests. One of the most special of the SS-Rank materials is the Brave Stone, which is used to evolve equipment from S-Rank to SS-Rank.