I have been replacing my own cartridge material pretty much since I started vaping. I have found it to be a pain. I did find a much easier way. I bought a bag of "Extra Loft Poly Batting". I got a craft size bag (36"x45"). It's the smallest bag you can get and runs about $10. You will have enough matierial for you and your friends for years to come. This is the batting used for making quilts and such. Instead of coming in a bag as a huge ball of poly-fil it comes in a bag as a roll of flat material. It is standard poly-fil and untreated. I cut a tiny strip to whatever width I need to fill the cartridge (about 5/8 inch for a 510). Then I cut the strip into 1/4 inch pieces. Now I have tons of 5/8 by 1/4 inch strips. Each one of these is perfect to fill a cartridge. No rolling or folding needed, and the wicking is fantastic. This makes for perfect density. If you make your strips too long just trim off the top til it's flush with the cartridge.