Genuine OEM HP Deskjet 1100C Ink and Supplies
The 1100C's HP 45 black twin pack contains two identical ink cartridges. It gives you a spare black cartridge, but doesn't include the separate HP 41 tri-color ink used for color printing.
Toner Buzz carries genuine HP 45 black singles and twin packs, along with individual HP 41 tri-color cartridges. Choose the black pack size you need, then add HP 41 separately when you also need color ink.