Tesla launched its robotaxi service in Austin on Sunday as its Model Y vehicles drove around a select batch of riders who gave rave reviews about smooth, convenient rides that were available for the cheap price of $4.

The company debuted its autonomous ride-hailing service Sunday. The limited program is invite-only and uses around 20 cars—signs that Tesla has a long way to go to catch up to its robotaxi rivals.

Tesla has launched its much-anticipated robotaxi pilot service in Austin, Texas. This milestone represents a significant step in the autonomous vehicle industry as companies race to deploy self-driving technology commercially.