the true HP cartridges can not be refilled and actually work properly due to the micro chip that is in them.
I have refilled mine, but after about 3 times, they are done..
I get my ink from a guy on ebay...really worth it...
I just have to remember that when I spend the day printing I have to refill right away..if you let them go empty, they will not refill properly!
no matter how you look at it, HP ink is terribly costly!