Patented Technology: Hand-polished inside the shaker container creates a more mellow finish on the mouth of the cocktail. The metal polishing technology used by automotive parts manufacturers in Toyota City, Aichi Prefecture.Artisan handcrafted technology with accuracy as much as 0.1 microns.The Birdy Cocktail Shaker has been hand polished to the inside of the container for a smooth mouth.Its advancement is not only captivating famous bartenders, but also bartenders worldwide.