Shift Premium Bluetooth Audio is a codec developed by Jaybird for decoding the audio with an enhanced bit rate. The result is crystal clear Bluetooth audio, which rivals leading wired headphones. PureSound filters out and eliminates white noise, delivering a clean audio experience, offering hours of pure enjoyment while eliminating listener fatigue. X2 patented sports ear fins hug into the top, back & lower surface areas of the ear, all essential to lock in for sports. X-Fit allows for your buds to be used either in the under-ear style for music & calls, or over-ear, designed for those wanting a great sports music experience. The patented secure fit ear fins utilize a proprietary hexagon cushioning for maximum stability, cushion and comfort for the longest adventures. Pack an incredible 8 hours of play time, enjoy a full day of music and calls, or work out an hour a day for an entire week on a single charge. Having voice on board makes for a great user experience. With voice prompts, getting to your first track is so smooth and simple.