PEI, Porcelain Enamel Institute, is an abrasion resistance rating that determines the durability and strength of ceramic tiles. The higher the PEI number, the more resistant the tile. Here are the different PEI rating classifications: PEI 1: Use for walls only. Tiles in this class are not suitable for floors. PEI 2: Use for floors with light traffic, such as bathrooms or bedrooms without direct access to the outdoors. PEI 3: Use for floors with moderate traffic, such as kitchens, living rooms, or entryways without direct access to the outdoors. PEI 4: Use for floors with heavy traffic, such as entryways, hallways, covered patios, or light commercial spaces. PEI 5: Use for floors with very heavy traffic, such as commercial spaces, airports, or shopping centers. ------------------------------------------------------------- The shade also called V Value is an index of variation in shade both in color and pattern that can be expected from a batch of tiles. Here are the different classifications of the V value: V1 (Very Low Variation): Minimal differences. The tiles are almost uniform with very little variation. V2 (Low Variation): Slight variations in color and pattern. The differences are noticeable but remain homogeneous. V3 (Moderate Variation): Significant variations. The differences in color and pattern are more pronounced but each tile is in harmony with the others. V4 (High Variation): Strong variation in color and pattern. Each tile can be very different from the others, offering a unique and dynamic appearance.