This is an insert for nerf darts. You can use this for older darts to avoid jam in your nerf gun. It works also for manual nerf guns. This is changing balance point of the dart and might affect the flight stability. For me it works great. Please give reply and tell about your experience with this tool.brim is by design. designed for 0.25mm nozzle perimeter width about 0.35mm put the whole tube inside of the dart and fix it with superglue