My 2 sons & I regularly/successfully refill our HP cartridges, the model 27 (black) and 28 (colour) do need resetting but (unlike Epsons) no hardware is required to do this, apart from 2 small pieces of sticky paper. A £10 kit of 3x30ml colour and 3x30ml black with syringe etc is a big saving, especially with the small 27 & 28 cartridges.
MikeD