The Mi Smart Band 4 features a 39.9% larger (than Mi Band 3) AMOLED color full-touch display with adjustable brightness. With music control on the band, you can change the song, increase or decrease the volume and groove on without even touching your phone. Up to 20 days of long-lasting battery life for uninterrupted performance. Style the band display as per your mood with unlimited watch faces. Simply pick a photo from your gallery and set it as your watch face. 30+ features rolled into one band, your perfect companion.