A spare collection ball is especially handy for brewers who want to harvest and re-use their yeast. The first yeast to settle out is the healthiest. After your yeast has settled simply remove the collection ball and replace it with your spare one. Then put an airlock in your collection ball of yeast and keep it in the fridge until you are ready to use it. A simple and sanitary yeast-harvesting system that will give you healthy, uncontaminated yeast for your next batch.