I just wanted to share this very simple technique : cut common empty spools into halves and glue them on the sides of Esun refills, to spare some plastic.

The majority of my 1kg spools have a 90mm small diameter that fits perfectly inside Esun refills (92mm inner diameter). I just leaves room for a 1mm thick layer of hot glue in between. The spools' height is also slightly smaller than the refills, so the two sides can actually touch the refill.

Assembly

• Cut the spool in two on the seam using a hacksaw, sand and clean the halves thoroughly
• Apply four spots of hot glue inside the spool, close to the top, between the plastic stripes (avoid stringing with the glue gun), and insert one half
• Repeat with the other half
• Cut and remove the plastic stripes