Only that it's a PITA to refill the 45. Unlike most other ink carts,
this one (and a few other HP black carts) uses vacuum. You need to
thrn the ink cart so the nozzle is facing up. Then remove the little
black sticker and puch in the little metal ball to access the ink
chamber and refill them. To reseal it, you need a new steel ball the
right size, squeeze the tank while you push the new ball in to seal in
and build vacuum.
There are tool that refull the 45 by forcing ink through the nozzle
but I haven't tried that so I don't know how well they work.