My dad was looking at the I-SAM tennis ball machines, just the base models. They do 15-60 mph, weight around 30 lbs, hold like 200 balls, and don't do spin. They oscillate and can do lobs i believe. If he intends for me to improve greatly with it, shouldn't i be working with a faster speed, and spin? I'm a 4.0 right now, but if i'm going to jump to 4.5 and HOPEFULLY a 5.0 eventually, won't i need something to simulate the strokes i'll be facing? The base model w/o spin and that only tops out at 60 is like 650-700$, with the version firing 85mph and having spin is like 1000-1100. Personally i think that it's a big investment, and since it's only 10 lbs heavier, carries more balls, shoots faster, and can add spin....that we should just wait until i can save up for the remaining money and buy one. I won't be using it over the winter much, so i have plenty of time.