Sometimes there’s a nuanced, almost invisible reason two companies should unite as one. Occasionally, an investor — professional or amateur — has special insight as to why two organizations could team up and achieve a synergy nobody saw coming. This is not one of those times. Wireless carriers T-Mobile US Inc (NASDAQ:TMUS) and Sprint Corp (NYSE:S) should merge to take on powerhouses AT&T Inc. (NYSE:T) and Verizon Communications Inc. (NYSE:VZ), and it’s not hard to figure out why.

On the chance not everyone knows all there is to know about the nation’s third- and fourth-largest (a distant third and fourth) carriers though, here’s a look at the three key benefits of such a pairing.

Three Ways T-Mobile Stock Would Win

This isn’t the first time owners of S stock and TMUS stock have heard about the possibility. Indeed, the notion of Sprint and T-Mobile has been circulating for a while. Most investors have quietly given up on the idea simply because it arguably should have happened by now if it was going to happen at all.

As they say though, things change.

Two weeks ago, Verizon delivered news that rattled owners of TMUS stock and Sprint shareholders alike — it was re-introducing unlimited data plans, forcing other carriers to do the same or suffer the consequences.

Problem: Verizon can afford to make such an offer, and AT&T can afford to counter. Sprint and T-Mobile, however, can’t … at least on their own. If they were working together, however, they’ve got a fighting chance. Three major upsides would make the two a formidable pairing.

1. T-Mobile’s Salesmanship

It’s actually rather amazing when you think about it. Despite the company ranking last among the big four carriers in terms of quality of its service during the second half of last year, T-Mobile continues to outgrow all of its rivals in terms of adding new subscribers.

Specifically, RootMetrics gave Verizon the highest marks based on quality for the latter half of 2016, with a score of 93.9. T-Mobile scored a mere 81.2. The next nearest contender was Sprint with a score of 84.7. Yet, TMUS topped them all in terms of membership growth, picking up 1.2 million postpaid subscribers in the fourth quarter alone. That’s almost as many new subscribers all the other carriers picked up combined.

2. Sprint’s Spectrum

It has been one of core justifications for owning Sprint shares, even through troubling times — it owns far more than its fair share of spectrum, even if it’s not using it yet. Indeed, the company may not even quite know how to use the bulk of the licensed frequencies yet, most of which sit at the higher-end of the frequency scale that hasn’t always been a concern of companies making wireless telecom equipment.

It’s becoming increasingly important though, not just because we’re running out of room at the lower range of approved radio frequencies, but because these higher frequencies in the 2.5 Ghz area are better suited for data-based transmission.

Sprint controls more high-frequency spectrum than all the other major carriers combined. T-Mobile, on the other hand, has very little high band spectrum.

3. Sprint Has Great 5G Infrastructure/Technology

It’s arguably reason No.2B as much as it’s reason No.3, but the reality is the same either way — Sprint is further ahead in the development of its 5G (fifth generation mobile broadband) technologies than T-Mobile could even dream about being.

Giving credit where it’s due, owners of TMUS stock have watched T-Mobile’s chiefs play it cool regarding fixed 5G wireless networks, allowing AT&T and Verizon to duke it out on that new frontier, and implying it would swoop in when the dust settles. A closer look, though, may clarify that T-Mobile just doesn’t have enough of its own infrastructure — fiber-optic lines, mainly — to do what Verizon and AT&T can do on that front.

Sprint, however, may have solutions and a workaround. For example, Sprint has been erecting multiple input, multiple output (MIMO) antenna arrays for a few weeks now, which could turn the aforementioned 2.5 Ghz spectrum into a very viable 5G network. AT&T and Verizon don’t have MIMO networks.

And that’s just one aspect of Sprint’s technology-intensive effort to lay the groundwork for growth. T-Mobile hasn’t invested enough time or effort in such matters.

Bottom Line for TMUS Stock

Don’t get the wrong idea. TMUS stock holders have to know there are still plenty of potential roadblocks ahead, not the least of which is the possibility that the Department of Justice’s antitrust watchdogs will nip any deal in the bud before it’s consummated. There’s also the not-so-minor matter of price; any organization that melds with Sprint is going to inherit $30.7 billion in long-term debt that the company itself is struggling to service.

Still, if deal can be done, owners of S and TMUS stock better hope it gets done. Verizon and AT&T both just indicated they’re willing to sacrifice profit margins in order to gain market share. Neither Sprint nor T-Mobile have that wiggle room by themselves.

As of this writing, James Brumley did not hold a position in any of the aforementioned securities.