I bought a packet of 3 G40+ balls and I have to say, this is the weirdest ball I have ever tried in my career.
First, the sound of the bounce is extremely high pitched that it almost sounds like a cracked ball and honestly hurts our ears.
Second, the bounce is one of the highest ever. Bounces higher than normal plastic balls and even celluloid balls.
Third, the speed of the ball is extremely fast. Faster than normal 40+ balls. Literally feels like the speed of the 38mm balls but less spin. Definitely not normal.
Fourth, although it's extremely hard, it wears off easily. Your reaction to this might be: 'wha? Table tennis balls can wear off?'. I know, it might sound weird but after a few hours of playing, the ball sort of looses its grip to the ball and tends to skid across the table. Only capable of a few hours and it's done. Again, it doesn't break, it wears off, just like how table tennis rubbers do, but in a much much much faster scale.
Despite all these negative aspects, the only thing the ball shines in is the roundness and hardness. However, although its roundness and hardness is achieved, the basic fundamentals of table tennis balls in definitely not achieved.