This unit is built using a galvanized steel commercial dryer drum, driven by a fully sealed 1/2hp electric motor via a reduction drive. The drum and its bearings disconnect from the stand for transport and the motor and reduction drive lift off as well. Tension is kept on the belt by the the weight of the motor etc. Holes in the drum are about 3/8" or about 10mm. Put down a tarp, put your wheel barrow underneath and adjust the angle of the drum as required depending on how long you want the material to stay in the drum. Most stones, roots etc. fall out the open end of the drum into a garbage can or whatever you put there. It's easy to scoop out other stuff with your shovel. The pulleys were sized to give optimal RPMs. If your soil is too stoney or you want to mix in other material, this is probably the best way to do it: a shovel of your dirt, a shovel of topsoil/compost etc. and it gets mixed pretty well. Obviously the soils have to be dry enough to fall apart and fall through the holes. ;-) I've used it with good success, but not for years so time for a new home - rent it out to your friends and make it pay for itself?! Would cost several times this price to build now.