#6 Invisible is the same as #5 Invisible from some companies. My pulls usually fit on the #5.
Invisible Zipper or Concealed Zipper comes in 3 weights: #2, #4, #6. The coil is 2mm, 4mm or 6mm across the closed zipper coil.
2mm: Best in light weight fabrics, dresses that aren't very tight.
4mm: Use in medium weight fabrics for pillows, duvet covers, garments.
6mm: This is heavy duty for use in tight garments (wedding gowns), pillows in heavy upholstery fabrics, slipcovers. Some manufacturers call this "#5 Invisible". My pulls will still open & close this, just a bit tighter.
Pulls on Tape: The Elves in the warehouse put the pulls on the tape for you. $1.20 per pull which includes labor & the pull.
Pulls NOT on Tape: YOU put the pulls on to make the zipper tape open & close.
Invisible zipper by the yard is less expensive than a finished zipper & more easy to use because you only stock yardage & pulls, not all the different lengths of zippers. Easily cut to length. To secure zipper head, sew over the ends. (I have videos)
Invisible zippers have more limitations than standard coil zippers (what you would normally use for upholstery). It does NOT self-heal. As you close the zipper, pull the zipper closed with your hand then pull the head across the coil. I usually use my fore-arm to press my pillow together then gently pull the zipper head across the coil. For brides, use 2 people to take the tension off the zipper.
I've tried this in cushions up to a 4" box. These zippers are reliable up to 2" foam & wrapped with dacron, but 4" foam with dacron or down wrap is too much pressure on the zipper.