It is normal for men to be apprehensive if they first heard about the device. They would be glad when they learn that the X4 Extender system works effectively. X4 Extender is designed to fit men, without slippage, regardless of the size of their penis. Pro Extender The X4 Extender system was developed for comfort and for faster results. The X4Extender could be used longer by men because it is convenient, but also because it allows proper circulation of blood I the penis. With longer use, the X4 Extender works more effectively and produces faster results.