Just to be precise, I have taken the trouble to weigh the two articles: 264 grams for the Powerball 250Hz Pro and 505 grams for the Powerball 350Hz Metal Pro.
In addition to the significant difference in weight, needless to say that a Powerball plastic looks a toy compared to the metal, the more it is significantly large: 73 mm in diameter for the Powerball 250Hz Pro and 77 mm for the Powerball 350Hz Metal Pro. This has perhaps casually but for a good grip it counts, especially when you go up in the towers.
Small disappointment on arrival of the package, I expected to receive the Powerball 350Hz Metal Pro as a transparent display case, I had to be content with a rudimentary plastic packaging, too bad.
For a kit against "SP-01" is provided, it includes a wrist strap, a start string (very useful), and some spare parts.
In short I am very satisfied with this Powerball 350Hz Metal Pro but given the weight and considering the price compared to a basic model, I hesitate to recommend as first Powerball.
If you already have a Powerball 250Hz Pro (or equivalent), please, this is just great!
