What is a "denier," and why does it matter? Most horse rugs have a 600D, 1200D, or 1680D rating. The higher the denier count, the tighter the weave of the threads and the longer the fabric will last. How heavy should the rug be? There are rugs of different weights to keep your horse comfortable all year: Lightweight (with no fill) cotton blends, mesh, or net for summer days. Lightweight (up to 100 - 150 g) or medium weight (200 – 300 g) for cooler weather in spring and autumn....