Lightweight white, solid-color or printed plain weave, satin weave, or flannel cotton or cotton/polyester blends are the most common types of sheeting, although linen and silk may also be used, including in combination. Goose or duck down and other feathers are frequently used as a warm and lightweight filling in duvets, comforters and quilts. But such fill can protrude in part even from tightly-woven fabric, and be an irritant for many people, particularly those with allergies. Natural and synthetic down alternatives are marketed. Cotton, wool or polyester batting is commonly used as fill in quilts and down alternative comforters. These are less expensive and more easily laundered than natural down or feathers. Synthetic fibers are best in the form of thermofused (where fibers cross) batting. Thick-woven or knitted wool, cotton, acrylic or other microfiber synthetics, or blends of these, are typically used for blankets.