Hi, this is my first post in years
What everyone has said pretty much sums it up. They are hard, heavy and bad for the elbow. tretorn X + full bed of Luxilon big banger ALU spin is not good for the elbow.
I found that the longer you hit them for/ wear them in, the bouncier they get. Then, after the fur comes off the balls become like bouncy balls.
I'd recommend against them. They are good to use a 4 square balls though :P