Bee Propolis is a resin-like material produced by bees from the buds of poplar and cone-bearing trees and is used for the construction and protection of their hives. Propolis has been the subject of thousands of scientific papers and has been found to contain a variety of beneficial compounds including phenolic acids, flavonoids, diterpene, amino acids, and different vitamins / minerals. Most competitors advertise a 10:1 or 5:1 extract that is not standardized to contain any active ingredients. Double Wood offers the most potent propolis extract with 5% flavonoids.