The thin plastic walls will “cut” into your pubic pad at higher vacuum levels (above 5hg) and cause some discomfort, though it does come with sleeves which could mitigate the discomfort somewhat. It says it is 2.36 inches in diameter so unless your girth is 6”+ you could easily have your ball(s) sucked in - ouch. If the connecting tube on the ball pump, is 1/4 inch you can switch to an Harbor Freight brake pump with gauge and emergency escape valve if you want to get serious. However, the connector does not appear to be the standard male connector used with the better quality cylinders. You may also need to get one of these as well - usually $5 plus shipping.
That being said, I think the price and free shipping make it worth getting to play around with at low pressure, provided you keep your balls pulled away while starting your vacuum. I have a similar system (but it has 1/4 inch tube and a standard male connector) and I use the ball pump for water pumping with a quality tube. I also use the tube occasionally for pumping the whole package, including the balls. A nice alternative and avoids the dreaded doughnut because most of the fluid build up goes into the scrotum and provides a bigger sack for a day or two.