Make Same Width 
Make Same Height 
Make Same Size 
When you are sizing or aligning multiple objects, the Editor uses the "dominant object" to determine how the other objects are sized or aligned. When multiple objects are selected, the dominant object has green sizing handles; all the other selected objects have aqua sizing handles. The dominant object is the first object selected. To change the dominant object press the Ctrl key while clicking the left mouse button.
All selected objects will be resized to match the selected dimension of the dominant object.