Yeast Hulls (Energizer/Nutrient)

Yeast Hulls (or yeast ghosts)are the centrifuged "shells" of yeast - they are usually the first action when you have a stuck or sluggish alcoholic or malolactic fermentation. Yeast Hulls are essentially dead yeast cells that absorb auto toxic yeast by-products that could be inhibiting your active yeast or ML culture from doing their job - finishing your fermentation! 

As a side note, Yeast Hulls are included in the Fermaid K mix of nutrients to help prevent problem ferments from the onset. The reason you would not use Fermaid K for most stuck ferments is that Fermaid K contains DAP. If DAP (Diammonium Phosphate) is added to the ferment past the point of metabolization by the yeast it could potentially leave an unwanted, residual flavor.
Use yeast hulls at the rate of .5 to .9 grams per gallon. If stored in a cool, dry place, will last up to 3 years.

A rough approximate of weight is 1 tsp = 2 grams.