It really works. Three fasteners for this price for more security!! Simple solution to clasp problem with Fitbit Flex. Clasp comes loose and you loose your device. It happened to me so I found this simple solution. Use these small fasteners by sliding them over the clasp. They stay on and are easy, quick and it works. This small investment will save you the cost of replacing your device. Comfortable - can't tell it's there. Be sure to order for FitBit Flex (Force is available in another add) as they are different sizes. See video on youtube, search for fixfitbit.