Complex sentence: In the summer of 2007 a new model of Powerball was created: the Powerball Screamer, which was made of Powerball 250Hz model and features 8 holes, drilled in the rotor itself.
Split into simpler sentences: In the summer of 2007 a new model of Powerball was created called the "Powerball Screamer". The Screamer is based off the Powerball 250Hz model, however, it has 8 holes drilled in the rotor itself.