Genuine OEM HP DeskJet 720 C Ink and Supplies
The 720C's two-pack ink choices serve different needs. The HP 45 twin pack gives you a second black cartridge to keep as a spare; the HP 45/23 combo pairs black with one tri-color cartridge.
Toner Buzz carries genuine HP 45 black and HP 23 tri-color ink individually and in those packs. Choose a single HP 23 when you only need color ink, rather than buying a black-only twin pack or both ink types together.