A stir bar is definitely something you'll want to have a spare of! Seasoned homebrewers know the value of being prepared and having spare parts. This 1" magnetic stir bar works great as a great backup or as a replacement.
Whether you need to make an extra starter, or you accidentally pitch the slurry with the magnet bar still inside, or just plain lose it you’ll be relieved to have an extra magnetic stir bar on hand.