The hearing aid sweat band is a small “sock” that protects the hearing aid from moisture and dust. It also fights feedback due to wind. It is disposable but will withstand a few launderings with a mild detergent and air drying. Comes in six colors and sizes are:

Mini (1”), Small (1 ¼”), Medium (1 ½”), Large (1 ¾”) and Ex-Large (2 1/8”)