The Ninja Paintball MagnaCap. Introducing the Ninja MagnaCap! Tired of losing fill nipple covers? It won't be a problem anymore. Ninja Paintball has created a super strong neodymium magnet cap that holds tight to your fill nipple, making these caps stay on no matter what. It's easily removable to fill, so no more struggling with stubborn rubber caps. Get this simple but effective upgrade today!