Enough for 5 brews of 5 gallons. Used to be called creamy top, same stuff different name. For those who need to know it's Propylene Glycol Alginate. Derived from Kelp, which is a seaweed of course. It's classified as safe and has one interesting side effect which is that it prevents the absorbtion of Strontium.
Strontium 90 is one of the ingredients in nuclear fallout, named after the place Strontian in Scotland. Anything that prevents you absorbing it is a good thing! More proof that beer is good for you!