Inkmail is similar to pre-paid phone card, only for inkjet cartridges. You purchase postage paid mailing boxes and use them to return your empty ink cartridges to our state-of-the-art remanufacturing facility. Once remanufactured and machine tested, usually in 72 hours from the time of receipt, the ink cartridges are returned to you filled with ink and ready for use. For use with: HP PhotoSmart: 8450, 8150, 2710, and 2610 HP PSC: 2610 and 2710 All-in-One HP Officejet: 7410, 7310 HP Deskjet: 6840, 6540, 6520, and 5740