There are two main reasons they collect grass very well. 1)  Highly efficient cutting deck design and 2) aerodynamic blade design. Grillo spend a lot of time and money studying ways in which to maximize efficient cutting deck operation while using the lowest engine horsepower possible. As a result, the grass is cut in long lengths and delivered to the collection bin without the need for fans or turbines. The finished result is excellent with no debris left on the lawn.