Whey Protein Isolates are 90% pure protein by weight. They are the purest and most expensive form of whey protein that exists. That's why they are the first ingredients you read on the 100% Whey Gold Standard label. By using Whey Protein Isolates as the primary protein source, Optimum Nutrition have been able to pack 24 grams of the purest, muscle-building protein per serving, with a lot less of the fat, cholesterol, lactose, and other stuff that you can do without. There's no question this is the standard by which other whey proteins are measured.