4 mm Silicone Plugs for Older HP Inkjet Refill 15, 45 (6 PCS)

Fits most HP models which has plastic ball

6 premium plugs per package
Outside diameter (OD) is 4 mm. Fits older style (e.g., HP 15, 45) 3 mm hole black HP cartridges has a plastic ball for ink-filling spot
Drill a hole or use a nail and hammer knock the ball inside, refill then plug the hole
Premium grade silicone guarantees a tight seal and longlife. Easy removevall for refill in the future
Easy removevall for refill in the future

Have you ever wonder how to refill those expensive HP cartridges? HP cartridges have a refill spot (e.g., HP 15, 45), sealed with a plastic ball. Get a nail and hammer to knock the ball in, refill it and seal it with this 3 mm silicone plug. Next time, just unplug and inject more ink.