ZDNet reviews the latest smart ring technology from Oura, comparing the Ring 3 and Ring 4. The new Ring 4 features receded sensors for improved comfort, expanded sizing options, and longer battery life. However, the Ring 3 still offers a lower price point and similar software updates. Which one should you buy? It depends on your priorities: comfort, size range, or daily charging.

Source: https://www.zdnet.com/article/oura-ring-3-vs-oura-ring-4/