#2 or 2mm Invisibles for Clothing
The lightest weight invisible zippers are #2 or 2mm across the invisible coil. This is the size you normally find in fabric stores for use in apparel.
I stock this size as replacement zippers for all those broken dress zippers in your closet. Unfortunately, garment manufacturers haven't figured out that their garment, as well as their reputation, is only as good as how long their zipper lasts. But on the other side, it keeps all of us seamstresses in business!
These are exceptional quality zippers! However, invisible zippers are not as strong as a standard coil zipper. Your zipper might have popped because of stress on it. In that case, you might try a #4 or 4mm invisible (a little heavier & harder to pop) or a standard coil #3 zipper as a replacement.