#4 Invisible Zippers work in skirts, pillows and duvet covers. Like all other zippers, the higher the number, the larger the coil. #2 is standard for apparel or what you would find in an fabric store. Invisible Zipper by-the-yard is #4 or a little heavier.
These zippers need to have sufficient tape to roll the teeth to the back of the zipper. If you sew too close to the teeth or over the teeth, these zippers will pop.
You may purchase up to 10 yards with the pulls on. We no longer put the pulls on 25 yards because the rapid movement of the pulls down the tape can damage the coil.