Yes, the Oura Ring 5 is noticeably smaller

From top to bottom: Oura Ring 5, Oura Ring 4 in ceramic, Oura Ring 4 regular, and Oura Ring Gen 3. This is not an Oura Ring 5 review. That's coming later, once I've had enough time to really test the new durability and battery life claims, plus the new software updates that start rolling out today.