The Fitbit Air itself is a small plastic puck about 1.4 inches long and 0.7 inches wide. It slots into various bands that hold the bottom-mounted sensors against your wrist. There’s no display pointing upward, so the entire device is covered by the fabric or plastic of the band. It’s a streamlined and potentially stylish look—in uncharacteristic fashion, Google has plenty of colors and style options available, including a special-edition Steph Curry versio