SpO2 sensors, which enable blood oxygen monitoring, were one of the marquee upgrades when Oura announced its third-generation smart ring. The only catch was that, even though the new Oura Ring had the necessary hardware, the feature itself was still in the works. Now, roughly nine months after launch, Oura says blood oxygen sensing will finally start rolling out to users this week.

Blood oxygen metrics have become increasingly popular when it comes to sleep tracking. It generally works by shining a red LED onto your skin. The amount of light that’s then reflected back is used to estimate how much oxygen is in your blood. The feature works similarly on the Oura Ring Gen 3, which uses a combination of red and infrared LED sensors. But while many devices — like the Apple Watch and the Samsung Galaxy Watch 4 — opt for spot check readings, the Oura Ring will take continuous SpO2 measurements during sleep.

Oura says users will see their blood oxygen data in the form of two new metrics: average blood oxygen and breathing regularity. The former is a straightforward percentage, while the latter is meant to track “observable drops in average blood oxygen levels.” That, in turn, is meant to help users see how many sleep disturbances were detected in a single night.

Both metrics will be turned on by default, but users can toggle them on or off from the Blood Oxygen Sensing option in the main menu. The metrics themselves will be displayed in the Sleep tab, and suspected variations will be shown in a timeline broken down into 15-minute intervals. Each interval is represented by a color-coded line — dark blue for few variations, light blue for occasional variations, and white for frequent variations.

That said, users should take these metrics with a grain of salt. As with any wellness gadget, the Oura Ring isn’t meant to be used in a medical or diagnostic capacity. For instance, while frequent sleep disturbances may behoove you to check in with your doctor, it’s not an automatic sign you have sleep apnea or any other chronic condition. It’s also not a suitable substitute for a pulse oximeter. Essentially, this kind of wearable SpO2 data is a relatively passive metric that doesn’t fluctuate much on a daily basis. Features like this are more or less meant to help you keep track of when your long-term trends deviate from your individual baseline.

Enabling the feature also comes with a few caveats. Oura specifies that blood oxygen sensing will be limited to sleep sessions lasting longer than three hours. The company also says that enabling SpO2 sensing will cut into the ring’s battery life. The Oura Ring Gen 3 has an estimated weeklong battery life, but over the past nine months, I’ve generally gotten around 4-5 days on a single charge.

Ultimately, it’s encouraging to see that Oura is finally delivering on many of the Gen 3’s promised features. (It also recently rolled out workout HR tracking, another feature that was absent at launch.) This is especially true since Oura introduced a new $6 monthly subscription for the Gen 3, and as you might expect, it wasn’t a popular decision among long-time customers. While the sting of having to pay a subscription won’t go away, it’s a small consolation now that users are getting more of what they were initially promised.