Ext.fly uses the Flyweight pattern, which basically means that instead of creating a new instance of Ext.Element to wrap around the DOM element, it uses one global instance of Ext.Element and just simple replaces the internal pointer to the DOM element within that instance. This makes it faster because it can skip constructor and additional logic to create the Ext.Element instance, and smart because it doesnt need additional memory for a new instance. To read more about the Flyweight pattern, you can read here: http://en.wikipedia.org/wiki/Flyweight_pattern