Citricidal® is the strongest form of Grapefruit Seed Extract you can buy on the market. There is no such thing as just the Grapefruit Seed Extract compounds by themselves. There must be a concentration. Therefore, in a sense, Citricidal® is the purest form of Grapefruit Seed Extract out there. This has a concentration of 60:40 Grapefruit Compound: Glycerin. The Nutribiotic Grapefruit seed extract is made up of the pure Grapefruit Seed Extract called Citricidal®. 1/3 parts of the Nutribiotic Grapefruit extract is Citricidal® and 2/3 parts glycerin. Therefore, for every three drops of Nutribiotic you have the strength of one drop of Citricidal®.