Crust leather is a type of leather that has undergone the initial stages of the tanning process but has not yet been dyed or finished. It is a semi-finished leather, typically light in color, and retains a natural, raw appearance. Crust leather is often used as a base material for further finishing, dyeing, or other treatments.

Key Features:

1. Initial Tanning: Crust leather has undergone the tanning process, which makes it durable and resistant to decomposition, but it still lacks color and finishing.
2. Natural Appearance: It retains a natural look with visible grain patterns, imperfections, and texture, which can add character to the final product.
3. Versatility: This type of leather is used in various products, including shoes, bags, and upholstery, as it can be easily customized with dyes, paints, and finishes.
4. Softness and Flexibility: While crust leather is not as soft as fully finished leather, it is more flexible than fully tanned leather, which makes it suitable for crafting and further treatment.
5. Customization: The unfinished state of crust leather allows manufacturers to apply different types of finishing processes like waxing, oiling, or coating for desired qualities such as shine, smoothness, or waterproofing.

Crust leather is often favored for products where the final appearance and finish are customized, providing a balance between the raw, natural leather and fully processed, finished leather.