T-Mobile disclosed a major new spectrum deal with Sprint that the company said stands apart from the two carriers’ plans to merge.

However, details of the new transaction are vague at best.

“In September 2018, we signed a reciprocal long-term spectrum lease with Sprint that included a total commitment of $533 million and an offsetting amount to be received from Sprint for the lease of our spectrum,” T-Mobile wrote in its latest quarterly filing with the SEC. “Lease payments are expected to begin in the fourth quarter of 2018. The reciprocal long-term lease is a distinct transaction from the Merger.”

Brian Goemmer from AllNet Insights & Analytics, a firm that carefully tracks the FCC’s spectrum licensing activities, said that, so far, the agreement hasn't turned up in filings at the FCC. But he said that, with a $533 million price tag, “it should be a pretty significant number of leases.”