The ATH-CKS550XiS in-ear headphones feature 9.8mm Solid Bass HD Drivers specially designed to fit within the headphones’ compact housings, giving you a comfortable listening experience that doesn’t sacrifice sound quality. The accurate sound reproduction is furthered aided by large-diameter sound tubes that extend frequency response for excellent wide-range audio with invigorating bass. The headphones are even capable of reproducing Hi-Res Audio sources.