New data shows that the latest generation of wireless technology is only available less than a third of the time in the best-served states.

A comparison study by OpenSignal released Thursday found that its testers connected to T-Mobile 5G only 34.7% of the time, AT&T 16.4% of the time and Verizon only 9.7% – and that’s generally not for the fastest 5G many had hoped for.

The reality is in stark contrast to what carriers say in their ads about 5G, which shows how much they rely on 5G as a selling point in the hotly contested mobile services industry.

T-Mobile advertises that it has “America’s largest, fastest, and most reliable 5G network,” with a map covered almost entirely pink, showing broad coverage. The map does not say what kind of 5G a user gets, but the fine print says it’s a mix of lower-performing versions. Top-performing “ultra capacity” 5G coverage, meanwhile, is only available in major cities and for several millions of people instead of most of the nation.

AT&T touts the “most reliable 5G network,” citing a test conducted for AT&T by Global Wireless Solutions that evaluates cellular networks. The company mentions, however, that its high speed 5G+ is only “available in select high-speed zones and venues in over 20 states across the U.S.

The BBB National Programs’ National Advertising Division has lambasted claims of all three companies about 5G, including one in August that prompted Verizon to change its statement that it was the “most reliable” to indicate it was not specifically referring to 5G services.