When I met on the internet in this refill, immediately realized the only way ... Of course, this new writing instruments for school children need also "feed" and what do you start with a 3-Piece Pack with two children? The same is not enough time and then must already ran the next. As you will be well served with this. For the equivalent of about 5x 3-piece-packs (price approx 1.80) you get instead of 15 cartridges in the pack 20. This also facilitates the refilling if the stock holds up longer. And Amazon delivers fast as ever. My recommendation to buy.