A proprietary blend is a group of ingredients listed on a supplement label under a single name with only the total combined weight disclosed — not the individual dose of each ingredient. You know what's in the product, but you have no idea how much of each ingredient you're actually getting. It's legal, it's widespread, and it's the single biggest obstacle to making an informed supplement purchase. Do Vitamins has never used a proprietary blend and never will — every ingredient and every dose in PurePump is fully disclosed on the label.