Details
Due to the disposable element of the cartridges, they come without warranty.
For best results use drip tip with cartos for easy topping up with liquid.
Other Re-filling Instructions:
This is the easiest way to fill up cartos, using the rubber cap that comes with them.
Here's a vid - don't forget to wipe off any excess liquid, especially at the battery end -
And here is the technique again, more in depth & detailed -