The NanoSPARK Flint Kit includes 5 replacement flints and 2 replacement O-rings. Fresh flints will keep the NanoSPARK providing maximum performance. As the flint wears, the performance degrades linearly. Flints are very easy to replace. Unscrew the tinder capsule and remove the QuickLIGHT tinder. Then unscrew the small brass screw, being careful as it is spring loaded. Remove the spring and tap out the remainder of the flint. Place only one new flint into the hole, then place the spring into the hole and slide the brass screw onto the spring and screw it all back together. If the old flint gets stuck and is worn down sufficiently, you may place another flint behind it. If the old flint is too long, the spring will bind when attempting to screw it back together. Simply remove the new flint and continue to wear down the old flint until a new one will fit behind it. Extra flints may be stored in the NanoSPARK tinder capsule below the QuickLIGHT tinder. Approximately 5 extra flints will fit. Ferrocerium flint works when wet. Up to 500 fire-starting strikes.