When storing your sunglasses use the microfiber pouch provided. To wipe off dirt, dust, smudges, etc..make sure you use the microfiber pouch provided or any other piece of clean microfiber. If they are covered in salt water, run them through clean tap water in your sink before wiping them down to prevent the salt and sand from scratching the lenses.
Do not use regular cotton or anything else besides microfiber! Cotton and other fabrics with thicker fibers pick up dust and dirt and can scratch your lenses if used! If your shades are super grimy, wash them with dish soap and warm water.