It might’ve taken a little longer than the company had hoped, but T-Mobile is finally ready to unleash its new “Digits” product. First teased all the way back in October 2015 when a T-Mobile executive fired shots at AT&T’s just-announced NumberSync, T-Mobile eventually introduced Digits as a beta this past December. That beta has now hosted tens of thousands of participants according to Evan Feldman, T-Mobile’s director of product marketing, and the company is ready to make it available more widely.

In fact, T-Mobile is announcing on Thursday that Digits will be made available to everyone beginning May 31st, and every single subscriber will have his or her phone number transformed into a Digits number for free.

So, what exactly is a Digits number?

In a nutshell, Digits is a nifty service that combines the best features of services like Google Voice and AT&T NumberSync into a single product. It allows one phone number to work on multiple devices, and it also allows one device to support multiple phone numbers.

The first part — one phone number that works on multiple devices — means that users can have their phone number function across any phone, tablet, wearable, or PC. For example, you can start a text chat on your phone and then pick up right where you left off on your PC when you sit down at your desk (just like Apple’s iMessage). Then, if you move over to the couch, you can chat on your tablet.

Another great use case is having one Digits number that rings a subscriber’s cell phone, his office phone, his wife’s phone, her office phone, and the couple’s home phone. That Digits number can then be given to a child’s school to ensure that someone will always pick up when the school calls.

The other main piece of the Digits puzzle is the ability to have multiple Digits numbers on one device. Again, there are a plenty of use cases here, but the obvious one is people who carry two different phones for work and personal use. More than 30 million Americans carry multiple phones, according to T-Mobile’s data, but Digits allows them to carry one phone that can support both numbers and pull double duty.

Another good example is creating a “burner” number you can give out when you sell something on Craigslist. Once the sale is completed, you can deactivate the number and not worry about getting calls from random people or from telemarketing companies that might have scraped the site.

Beginning next week on May 31st, every single T-Mobile phone number becomes a Digits number. That means in addition to your main smartphone, you can also use it for voice calling and text messaging on any Android phone, iPhone, iPad, Android tablet, wearable, or computer. This applies to all subscribers on all T-Mobile plans, postpaid and prepaid alike.

Subscribers on a T-Mobile One Plus plan will get a second Digits number free of charge. Note that this won’t happen automatically, however — you’ll need to call customer care or go to a T-Mobile retail store in order to activate your second Digits number for free, and this offer is only available for a limited time.

For everyone else, or for One Plus plan holders who want more than two Digits numbers, each additional number costs $10 per month. More information can be found on T-Mobile’s website.