Project Fi puts you on the best available network between Wi-Fi and two 4G LTE networks. This means you get access to more cell towers and 4G LTE in more places.

Project Fi has partnered with Sprint and T-Mobile, two of the leading carriers in the US, to launch our service.

simple plan starts with the Fi Basics for $20/month. It includes unlimited domestic talk and text, unlimited international texts, Wi-Fi tethering to use your phone as a hotspot, and access cellular coverage in 120+ countries.

Project Fi only available on the Nexus 6P, Nexus 5X and Nexus 6.

https://fi.google.com/about/faq/#plan-and-pricing-1