Off-white The appeal of flannel includes its high heat retention and light, comfortable feel. Because it's warm, it's one of the essential fabrics for the cold winter months. The fabric used is flannel, a light, soft, and very smooth material. The secret to its feel is a cover made of fabric woven with high-density, ultra-fine microfibers. It doesn't feel cold when you get into bed, and you can feel the warmth immediately. With its cozy warmth, it's an indispensable item for the cold season.