AT&T and Crown Castle International have announced a wireless tower deal totaling $4.85 billion. Under the terms of the deal, AT&T will lease 9,100 of its wireless towers and sell 600 of its wireless towers to Crown Castle. Crown Castle will acquire the rights to all of the towers, in exchange paying AT&T $4.85 billion in cash. Crown Castle will also have the right, at the end of the tower lease periods, to purchase those towers for an estimated $4.2 billion total.

Under the agreement, AT&T will be able to sublease extra capacity from the leased towers for the next 10 years at per month per tower rates that increase 2% annually. The mobile provider also has access to reserve capacity on the towers, and claims that the deal “will have no impact” for its network subscribers.

“This deal will let us monetize our towers while giving us the ability to add capacity as we need it,” said Bill Hogg, SVP of Network Planning and Engineering at AT&T. “And we’ll get additional financial flexibility to continue to invest in our business, maintain a strong balance sheet and return value to our shareholders.”

T-Mobile last year entered into a similar deal with Crown Castle, selling three decades of rights to 7,200 wireless towers to the company for $2.4 billion. Crown Castle International is the largest provider of wireless infrastructure in the U.S. The company operates around 40,000 wireless towers in the U.S., many of them in the country’s largest markets. Crown Castle also provides wireless coverage for nearly all of the Australian wireless market through around 1,700 wireless towers.

“We are very pleased with our agreement with AT&T, which strengthens our position as the largest provider of shared wireless infrastructure in the US, which we believe is the largest, fastest growing and most profitable wireless market in the world,” said Ben Moreland, CEO of Crown Castle. “Consistent with our focus on the top 100 US markets, nearly half of the AT&T towers are located in the top 50 markets, where we expect the majority of network densification and upgrade activity to occur.