Generic Compatible Ink Cartridge Replacement for HP 564 ( Black,Cyan,Magenta,Yellow , 4-Pack ) The prefilled cartridges can be used as regular ink cartridges for an easy using. The cartridge can be easily refilled and reused again and again. There are easy-refill hole and rubber plug on the top of each cartridge. The cartridge is transparent. It is easy to view how much ink left to prevent from lack of ink to cause air bubbles or how much ink filled in to avoid overfill for easy operation. These patented cartridges are environmental friendly, 3R (recycle, reuse, reduce) green products for endless inkjet printing with big saving.