This is a coagulant extracted from veal. It is widely used in the commercial cheese making industry to coagulate the milk for cheese and junket making.
1/2 teaspoon is enough to set 2 gallon of milk in about 45 minutes. To prepare mix the rennet need with 20 times cold un-chlorinated water. Then added the dissolved portion to your recipe as directed.
One 2 ounce bottle is enough rennet to set about 48 gallons of milk.