HP printer models using the HP C6615 (HP 15) black inkjet cartridges:

HP Deskjet 810c
HP Deskjet 812c
HP Deskjet 825c
HP Deskjet 825cvr
HP Deskjet 840c
HP Deskjet 842c
HP Deskjet 843c
HP Deskjet 845c / 845cvr

HP Deskjet 920c / 920cxi / 920cvr
HP Deskjet 940c / 940cvr

HP Deskjet 3810
HP Deskjet 3816
HP Deskjet 3820

HP Officejet V30
HP Officejet V40 / V40xi
HP Officejet V45

HP Officejet 5105
HP Officejet 5110 / 5110xi / 5110v

HP PSC 500 / 500xi
HP PSC 750 / 750xi
HP PSC 950 / 950xi / 950vr