Yeast Sachet Pack Size: 5g A small sachet of Yeast which can be used as a re-fill for the Philip Harris Drosophila Food Starter Kit.A small number of yeast granules are added to the surface of the food in Drosophila Food Tubes in order to activate.Please note that our Yeast is not to be considered as being of Food Grade Standard and is not fit for human consumption. It is only suitable for use in education.