I use HP 902 cartridges. I use the XL model for black and normal versions for colour. My black XL was almost done so I drilled a hole in the rear chamber, slowly filled it up until I saw ink at the top, then used tape to seal it. Everything went well and it works as usual (except you have to turn off the ink level indicator). Little did I know that a refill of black ink would be enough for an XL cartridge. I use black a lot more than colors. I'll have to see if I can just buy black refills