Google has announced that its mobile service, Project Fi, has become invitation-free. And, it is offering the Nexus 5X at a promotional offer of $199 exclusively for subscribers of Project Fi.

Project Fi was announced in April 2015. Currently, it is only compatible with Nexus smartphones like Nexus 6, Nexus 6P and Nexus 5X.

Google's Project Fi allows subscribers to seamlessly switch between cellular data connection and Wi-Fi hotspots on their smartphones. When the cellular data network is weak, Project Fi connects to the available public Wi-Fi connection to provide faster internet connection.

Project Fi makes use of T-Mobile and Sprint networks. Since the time it was launched, it was available on invitation basis, but now Google has officially stated on its blog that it can be availed without an invite.

The starting plan of Project Fi requires users to make a monthly payment of $20 that provides them unlimited talk and text messages. For every 1 GB of data, users have to pay $10 more. If a subscriber uses 2 GB of data, he will be charged $20 as the base amount along with $20 for the data. If the user only uses 1.5 GB of data, Google will only charge $15 for the data.

As Project Fi has become invite-free, in order to attract more subscribers Google has started a new promotional offer on the Nexus 5X. The smartphone is generally available at a retail cost of $349. However, with Project Fi, the Nexus 5X can be purchased for $199.

The LG Nexus 5X was released last year in October and it comes with the latest version of Android Marshmallow. It features a full HD 5.2-inch IPS LCD display, a Snapdragon 808 chipset and 2 GB of RAM. Other specs include 16 GB / 32 GB storage options, 12.3-megapixel rear camera, 5-megapixel front-facing camera, USB Type-C port, a fingerprint sensor and 2700 mAh battery.