Make sure geometry_msgs::Twist or cmd_vel units

edit

Hi all, I have confusion about the unit of geometry_msgs::Twist, are they m/s and rad/s? Because I saw the sample code turltebot teleop as well as kobuki teleop, they setup these parameters equal 1.0 for each press button. However I checked the specification of the turtlebot kobuki in this link , the maximum of linear velocity is just 70 cm/s, if my above opinion is right, the setup parameters in sample code is 100cm/s, it is overload the motor. So what is the true unit of geometry_msgs::Twist or cmd_vel?