Sensa-Spray works by surrounding your plants in a gaseous female hormone atmosphere. This incites your plants to produce supranormal levels of its own female hormones resulting in more female and less male flowers.The active ingredient in Sensa-Spray is ethylene, which a normal female plant would produce on its own. The reaction to an external application of this natural hormone is to shove the plant's hormonal consciousness in the feminine direction regardless of inherent genetics. Whether the plant was a natural male or female doesn't matter, the plant now responds to such treatment by producing its own elevated levels of ethylene. This may seem odd, but reallly isn't since all plants have the genetic machinery to create these hormones on their own. The only difference between males and females is the degree of genetic repression in allowing it to happen. Inherent females are enhanced, inherent males are sexually reversed. Hormonal inertia in the feminine direction continues until the time you harvest. Sensa-Spray is used at that time in the plant's life when it is still sexually uncommited. For indooor growers, this means before any change to the shorter light cycles. For outdoor growers, this means a few weeks prior to that time of year when you are first able to determine the sex of your plants. Sensa-Spray will redirect the plant energy away from vegetative growth and into the formation of vegetative female sex organs. Sensa-Spray is a unique product. It does not contain gibberellins, naphthoxyacetic acids, nor any other standard commercially available chemicals you are likely to encounter. What Sensa-Spray does contain is a compound which decomposes after dilution to yield ethylene in the proper and exact concentration to incite your plant towards feminization. And since it does decompose after it has done its job, Sensa-Spray is absolutely safe, both to the plant and to you. Makes 2 gallons of foliar spray.