The ES40 system is a simple yet precisely engineered system for the smaller openings where sliding windows are required. The reinforced interlock in this system gives the option to increase the height (when necessary) of these windows to withstand the wind pressure, to nullify deflection, and in turn the rattling noise that one has generally associated with aluminium windows. With the high number of glass options available one can easily accommodate these windows in their household without spending as much compared to the other systems and getting a similar performance.