Ultimate Listening Experience Using an accumulated ear shape database collected throughout decades of research, Sony designed the IER-Z1R for comfortable yet stable wear with an optimized housing shape, 13 variations of ear buds (six variations of triple comfort ear buds and seven variations of hybrid ear buds) and pre-formed ear hangers. This exquisite pair of headphones also boasts a zirconium alloy outer housing for increased hardness, corrosion resistance and durability.