Barz Optics black floating sunglass retainer is a strap with the most buoyancy and prevents loss of your valuable sunglasses. The leash has a toggle so that they can be tightened onto the wears head. Each end has a tube to help grip to sunglasses. This will suit small to medium sunglass temple ends. “Floats” on the retainer helps to float in salt and fresh water. It will have no issues with Polycarbonate, TAC or CR39 lenses glasses and should float even sunglasses with glasses lenses. However we would advise testing them in still water before you venture out into deep water.