I don't have a lot of experience with zippers, so normally I wouldn't respond, but I just installed a 12" No. 8 Riri zipper in a straight line. Before installing the zip, it wasn't as smooth as I'd hoped. After sewing it in, it works great. It doesn't feel like a No. 5, whose teeth are more numerous and close together, but I'm quite happy with it. Feels very solid and moves easily. For the casual backpack on which I used it, the large No. 8 is a good look.
Okay, so I found the problem. I watched this video. it cannot go on both ways. :D
I don't have a lot of experience with zippers, so normally I wouldn't respond, but I just installed a 12" No. 8 Riri zipper in a straight line. Before installing the zip, it wasn't as smooth as I'd hoped. After sewing it in, it works great. It doesn't feel like a No. 5, whose teeth are more numerous and close together, but I'm quite happy with it. Feels very solid and moves easily. For the casual backpack on which I used it, the large No. 8 is a good look.