The Oura Ring is a fitness tracker popular among athletes, business execs, and celebrities.Fitness reporter Rachel Hosie has used one for four years and was originally attracted by its look.Oura ``Rings provide sleep data, step counts, and menstrual cycle tracking.When I first learned about a new fitness-tracking smart ring four years ago, it wasn't the promise of high-tech features that most piqued my interest, it was the look.As someone who enjoys both fashion and fitness, I didn't think the wrist-worn devices I'd encountered as a health reporter, such as the Whoop strap, Apple Watch, and Fitbit, were attractive enough for me to wear all day every day, to everything from the gym to a wedding.But the Oura Ring, which just looks like a chunky band (mine is gold but other colors are available), was different.Four years later, the look is still important to me, but it's the increasingly clever features that mean I still wear an Oura Ring.Launched in 2013, the Oura ring's popularity has soared in recent years and can be spotted on the hands of athletes, business execs, and celebrities. Last December, the Finnish company announced that its valuation had doubled to $5.2 billion since 2022, thanks to $200 million in new funding. Various brands have launched their own smart rings in recent years but Oura still leads the pack.At $349 to $399 for the latest Oura 4 model, plus a $5.99-a-month subscription, it's not cheap, but neither is an Apple Watch, which can cost as much as $799 for the top model.A few years ago, people were always surprised when I told them my ring was an activity tracker. Now everyone from the saleswoman at a jewelry counter to my sports teammates ask me if I'm wearing an Oura Ring and what it's like.Here are the pros and cons of the Oura Ring that I've found after four years of wearing one. The Oura Ring shows all the data it collects on the app. Oura Con: You can't really wear an Oura Ring while weightliftingWhile the look of an Oura Ring is a big selling point to me, a wrist strap would be better for strength training, which is the bread and butter of my exercise.For movements like deadlifts and pull-ups, I take my ring off as it pinches my skin.However, I'm only interested in tracking the weights I use and reps in workouts, which trackers can't do and so I log separately.Pro: The Oura Ring tracks my daily movementsI love that my Oura Ring picks up all my movement throughout the day, including my steps (a metric the Whoop strap, for example, doesn't track). And it's perfectly comfortable to wear, say, on a run, which is when I like to know my heart rate.The Oura Ring can track various activities, and it's remarkably good at knowing what you've done, from cycling to rowing. It even picks up housework as an activity, which I think is a fantastic way to remind people that all daily movement, not just formal exercise, is important.It also picks up restful moments, including naps if I were much of a napper.Although my ring's battery life has slightly worsened with time, I only have to charge it for about an hour every few days.While some people like having a screen on their device, data collected by the Oura Ring is shown on an app. I like being able to check mine when it suits me. Jennifer Aniston has been spotted wearing an Oura Ring. James Devaney/GC Images Pro: Oura Rings provide detailed sleep dataOura Rings are generally considered to be among the most accurate wearables for tracking sleep, and it's really interesting to see not just how long I've slept in total but also the split between sleep phases, how long it took me to fall asleep, and the overall quality.Research by the University of Oulu in Finland found that the Oura Ring measures resting heart rate at 99.9% reliability compared to a medical-grade electrocardiogram. Oura supported the study by providing equipment and software, and some of the authors were employed by Oura. However, the company was not involved in the study's design or collection and analysis of the results.Shortly after waking up, I find myself reaching for the Oura app to see how I slept, rather than checking in with my body and seeing how I actually feel, which I don't think is a great thing.The sleep data is clever and interesting, but arguably unnecessary for the average person. Wearing a smart ring won't improve your sleep, but it can help you change your habits.Pro: The Oura Ring encourages you to rest Rachel Hosie likes being able to wear her Oura Ring with any outfit. Rachel Hosie Like the Whoop strap, the Oura Ring was one of the first smart devices not just to push people to move more but to help users balance recovery with activity. If you're not well rested, Oura will suggest taking it easy.I like that it promotes balance, but most people can only exercise at certain times and don't necessarily have the luxury of waiting for the next day when their Oura Ring might say they're in a better place to train.That said, it's no bad thing to factor in that perhaps you should do a slightly lighter session.Pro: The temperature sensors can tell you if you're sickOura Rings are very sensitive to body temperature, and this is one of the methods they use to determine when you're feeling tired and where you are in your menstrual cycle.These features are really smart I've heard various Oura users say their rings know they're going to get ill before they do, and studies support this. Similarly, mine has alerted me when my period is going to be a few days late based on my temperature.I take Oura Ring data with a pinch of saltWhile I do believe the Oura Ring is one of the most accurate wearables available, I also know to take all the data with a pinch of salt, and I won't live or die by what it tells me.This is what Livvy Probert, a personal trainer, sports scientist, and head of science at personal health assessment company Hawq Score, previously told me. Wearable tech like Oura Rings are great for monitoring your own sleep and activity trends and progress, but because accuracy can't be guaranteed, you shouldn't necessarily read too much into the numbers.