esr Black Standard Capacity Remanufactured HP Toner Cartridge 4k pages - C3903A esr is an extensive range of premium, remanufactured toner cartridges, offering high-quality consistent performance and significant cost savings compared to the manufacturerís original product. †We work to recognised international quality and environmental standards delivering a product which not only saves money but has been produced with sustainability at its core. All cartridges come a lifetime no quibble guarantee.