Sunglass lanyards are made by many different companies from a variety of different materials, including cotton, nylon/spandex, neoprene, and even plastic. All materials have their ups and downs, and what material works for a particular individual is highly reliant on personal taste. In a nutshell, cotton lanyards are often quite comfortable, but if they get wet, they can get heavier and chafe the wearer’s neck. Nylon/spandex lanyards are more weather resistant, but aren’t as soft on the ears, neck, and face as typical cotton ones. Plastic is cheap and efficient, but not all that comfortable and often not attractive. Neoprene models are available in many colors and styles but often tend to run a little higher in cost than the others mentioned earlier. In the end, find a material that feels good and looks good on you, and you’ll be more likely to be wearing it when your glasses slip.