Hash oil or cannabis oil is obtained by the extraction of cannabis or hashish. It is a concentrated form of the plant containing many of its resins and terpenes - in particular, Tetrahydrocannabinol (or THC), Cannabidiol (or CBD), and other cannabinoids. There are a variety of extraction methods, but most involve a solvent such as butane or ethanol. Hash oil is usually consumed by smoking, vaporizing or eating but sometimes other methods are employed. Hash oil is sometimes sold in cartridges to be used with pen vaporizers.