Eucommia bark (from Eucommia ulmoides) is the primary plant-sourced herb in Chinese herbalism used to tonify the Kidney Yang functions, in particular as it affects the skeletal structure. Although Eucommia is primarily known as a powerful Yang Jing tonic, it is also a strong Yin Jing tonic herb as well. Because it provides both Yin and Yang, it is a superb tonic herb for men and women alike and can be used by almost anybody to support the functions of the endocrine system, to support the physical structure, to provide foundational Jing for the reproductive system, and to support the immune system. It may be combined with any number of other tonic herbs in a formulation or tonic herbal program designed to build the Yin and Yang of the Kidney. Most extracts of Eucommia in the American market today are made with Eucommia leaves to reduce cost. The bark, however, is much more potent and is favored by connoisseurs of tonic herbs. Eucommia bark that has achieved appropriate maturity is extremely well balanced and chemically rich. Dragon Herbs uses only fully mature (10 years old or older) Eucommia bark in this important life-supporting, tonic product. The trees are sustainably harvested.