Attaching an end-effector .stl or .xaml file with a .xacro Industrial Robot and loading on Gazebo via ROS

Question

I have build an end effector with the use of the Rhino, where the file can be saved as an .stl or as an .xaml. I would now like to attach the end effector to an Industrial Robot, particularly the ABB IRB-120 Robot, and load it onto Gazebo. I have also managed to install the robot itself via ROS and the arm_controllers file.

The next step would to load the robot with the end effector, where I am referencing to http://wiki.ros.org/Industrial/Tutorials/WorkingWithRosIndustrialRobotSupportPackages

However, I noticed that the end effector in this case is a .xacro file. Is it possible to load a .xacro robot and attach an end effector made using a .stl file or a .xaml file?

Thanks in advance, Jacob