FINIS Duo 4GB Underwater MP3 Player. The Duo is an MP3 player designed for swimmers that offers the highest quality sound without the use of ear buds. The Duo utilizes a sleek, two-piece design and Bone Conduction audio transmission to deliver crystal clear audio through cheekbones to the inner ear. An integrated clip design secures the Duo to goggle straps to rest on the cheekbones for a comfortable and streamlined fit. And buy this FINIS Duo 4GB Underwater MP3 Player with Bone Conduction Audio Transmission Now £95.00.