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Protected Aniline Leather is top grain leather that is dyed for color and then receives pigment. This makes the natural imperfections of the hide less noticeable. The pigment also ensures color consistency, protects against fading, and helps the leather wear well over time. A clear water based topcoat is then applied for additional protection.
Semi-Aniline Leather is pure aniline leather that has a small amount of pigment or clear finish thus allowing natural characteristics of the hide to still show through while offering some of the benefits of color consistency and increased wearability.
There is also bycast leather, a.k.a. bicast leather or split leather. This leather is has a layer of polyurethane applied to the surface. The result is a less expensive, consistant textured leather that's easier to maintain than top grain leather.