Why do I have to pay for ROS MAX if I have already chosen ROS MAX head？

The ROS Max head refers to a series of heads that are compatible with the ROS Max functionality. However, each head still requires an upgrade to include the movable-jaw mechanism. You paid USD 180 for the upgrade on the first ROS Max head. The same rule applies to the second head. Without the upgrade, the head will be a ROS Max head in name only, without the actual ROS Max functionality.