WARNING: BIGGEST FILE EVAR.
Here's the tutorial I did for my shoes. Enjoy. If you have any questions, just ask.
Forgot to add the zipper link![link]
Buy the one without the pully thing.
I don't remember this site having different lengths when I bought mine. I measured my shoe, though, and I used around 14" of the zipper. I have very small feet, though, (I can't remember if I bought a size 5 or 6 in the Converse), so the length you need to buy all depends on your shoe size. I would get ATLEAST 18" to be safe, but again, it all depends on your shoe size.