The HP Laser Jet 78A M1536 is a compatible black toner cartridge designed for use with select HP printers. Specifically, it is compatible with models P1566 and P1606. This unit is ideal for those looking to replace their current toner cartridge with a high-quality and reliable option that produces crisp and professional-looking black prints. With its laser print technology, this toner cartridge ensures consistent and sharp results with each print.