Oura’s new Ring 5 is a massive upgrade for smart rings, dramatically shrinking in size and weight to bring them right into line with standard wedding bands and other jewellery. It is finally a smart ring you can genuinely forget you’re wearing.The Ring 5 is a straight replacement for the popular Ring 4 and costs from £399 (€399/$399/$A649), though it requires a £5.99 (€5.99/$5.99/A$9.99) a month subscription to access anything but basic daily metrics. An Oura is not a cheap proposition.The new ring is 40% smaller in volume than its predecessor, which was already one of the most compact smart rings on the market. Oura has cut the width to just more than 6mm, thickness to 2.23mm and weight to a featherlight 2g for the Ring 5. But numbers and pictures don’t do it justice; the Ring 5 looks and feels far smaller in the flesh than predecessors or any competitors.The difference in size of the Ring 5 (black) from the Ring 4 (silver) is dramatic in the flesh. Photograph: Samuel Gibbs/The GuardianIt is so much easier to live with: it won’t catch on pockets, dig in when you put your fingers together or hurt when you carry shopping bags or lift weights. And it looks even less like a piece of technology than the Ring 4, though that also makes it less of a conversation starter.It still records your heart rate, blood oxygen, temperature and motion to track more than 50 different metrics involved in your sleep, activity, readiness, stress, resilience, heart and women’s health. That allows Oura to comprehensively log and analyse your general health as well as the best smartwatches, but without the bulk of other wearables.The titanium Ring 5 comes in a choice of six colours and finishes, all with a harder, more scratch resistant coating than previous models to help it stay looking new for longer. In the weeks I’ve been wearing one, the black model still looks pristine even if it is not as hard as the ceramic Ring 4.The sensors stick out on the inside, but are not noticeable when wearing the Ring 5. Photograph: Samuel Gibbs/The GuardianIt comes in a choice of eight sizes, for which Oura provides a free sizing kit with plastic replicas that I recommend wearing for at least few days to find the best size. The ring has to be snug enough to stay put for the best data, but loose enough you can get it over your knuckle to charge it about once a week on the included dock or optional battery case (£99).Despite the ring shrinking in size, the battery life has increased by a day or so depending on size. The smallest Ring 5 should get about six days between charges increasing to nine days for the largest. The size 8 as tested – the third smallest available – lasted just shy of eight days or about two days longer than the equivalent Ring 4, which is a remarkable achievement.A full charge takes under 90 minutes using the included dock, but the ring is best charged a little bit each day such as when in the shower. A handy travel charging case with up to five full charges is also available. Photograph: Samuel Gibbs/The GuardianSpecifications