T-Mobile on Wednesday announced that it's again offering a family plan that provides 10GB of data each for four people at a cost of $120 per month. It's a great deal — T-Mobile said it's one of its most popular promotions ever — and here's how it works.

You'll first need to sign up two lines with 10GB each at $50 per month. After that, you'll sign up for two additional lines, each with 10GB of data. The third line will cost you $20 a month, while the fourth is "free." The total cost per month comes out to $120 before taxes. The plan includes T-Mobile's rollover data, calls to and from Mexico and Canada, international roaming and more.

The promotion is only available for a limited time, so hit the source below if you're interested.