@klizana Use heat (e.g. hair dryer set to low) to remove the ink sac. Be careful - if it's too hot for you, it's too hot for your pen! Dish soap, a toothbrush, and warm water can remove the remaining adhesive. Apply a layer of shellac where the old sac attached, use a pair of tweezers to help you attach the new inc sac, then give it a gentle twist. "Dust" the sac (unscented talc or corn starch) before inserting it into the barrel. Wait about a day for the adhesive to set..