The Strauss DO/F tumbler, 350ml, is composed of lead free crystal glass. Glass rim is toughened This formulation is called SON.hyx and gives the glass incredible clarity and transparency. Zinc and magnesium are added to the glass to give extra strength, compared with standard crystalline glass, which in turn is stronger than the everyday soda lime glass. The SON.hyx glass will retain its clarity for approx 4000 cycles in commercial dishwashers. Thus the SON.hyx formulation enables the glass to be nearly twice as strong as standard glass products providing high resistance to breakage and everday knocks. The Strauss liqueur has a rounded squarish thick glass base.