The machine is very heavy duty. So far so good I’ve only used fast balls and curved balls and the machine is awesome. Do not put any sort of synthetic Baseball in this machine or you’ll be spending some time cleaning the residue off of the wheels. It tells you right on there do not use synthetic. Tater balls or bata dimpled work best. You can use rail full grain leather baseballs, but they do get expensive and the faster you throw on the machine the more of a sting it is while you’re hitting.