B&W printing with special cartridges

Hi everyone,
I've herd some gossips about some special gray(?) cartridges for Epson(?) to make very high quality B&W prints. Is it true? Which printers and models use these inks? Did anyone's tried or seen these prints?
I've herd some gossips about some special gray(?) cartridges for Epson(?) to make very high quality B&W prints. Is it true? Which printers and models use these inks? Did anyone's tried or seen these prints?