Garmin v&iacute;vosmart 3, Fitness/Activity Tracker with Smart Notifications and Heart Rate Monitoring, Black The thinnest HR-equipped activity tracker from Garmin at 4mm thinner and more form fitting than Vivosmart HR; Strap material: silicone While not in use, the discreet display disappears into the device so as not to overshadow your style. Display size: 0.38 x 0.76 inches, Display resolution: 64 x 128 pixels Measures VO2 Max, which is widely recognized as an excellent measure of your aerobic fitness and should increase as your fitness improves Stress monitoring enables users to see periods of elevated stress or restful recovery New strength training activity will count sets, reps, and rest times and will push them to Garmin Connect for review