Denier characterize the strength of a material used for a horse blanket. A material with a higher denier number is stronger than one with a lower denier number. For example, a 1000 denier material would be stronger, more durable, and with better water repellent properties than a 500 denier material. The denier number is also known as the yarn fineness or the yarn count. The denier of a horse blanket is an indication of the thickness of the yarns.