For domestic use, not medical.
Two layers, one cotton and one poly cotton. If using Elastic two loops at 5 inches (13cm). If cotton tape’s, four lengths at 18 inches (46cm). It is possible to add a third layer of some non woven fabric inside. This could be baby wipes (washed) , vacuum cleaner bag fabric has been recommended, vilene or even paper towel. They can be used when shopping, when finding oneself in a place where social distancing is difficult, on public transport. Make two for yourself, one to wear and one to wash.