A couple of years ago, the Oura Ring 4 impressed us with its health tracking capabilities. Now, the Oura Ring 5 looks to do the same, but in a much smaller form factor. Oura officially unveiled Ring 5 on Thursday, bringing news that the device is 40 percent smaller than the previous model, making it Oura's smallest health wearable yet. It launches on June 4, starting at $399 for basic finishes like silver and black. You can pay an extra $100 to get it in the Gold, Stealth, Brushed Silver, or Deep Rose finishes, too. There's also a standalone charging case available for $99, but you'll need to get that separately. If the smaller size of the ring wasn't enough of a selling point, Oura is also packaging it with a bundle of new software features that sound pretty useful for health tracking.…