Here are pictures of the large brass (#10 YKK) zippers that I use on my custom and handmade leather goods. These are hand sewn in using 5 ply bees-waxed nylon thread. The holes for it are pre-punched and spaced about 1/4" apart. All of these pictures are clickable for larger views.
These are the #10 YKK brass zippers. Years ago I used smaller zippers, but, they were the first thing to wear out. Customers didn't like that and I didn't like having to replace them. I switched to larger ones and I have heard good things about them ever since. If there was ever a need, I could use other zippers.