I have two small rucksacks (bagpacks?), it's made of very light nylon, the sort you can fold away and keep at the back of a bike saddle. It's in some ways very well made, enforced with nylon webbing in all the the right places, solid enough click-in-place latches, cleverly made with compartments and functional shape.
The not so good are the seams, they slippery nylon unravels in places and the stitching is not the best. I have sewn over twice or more to enforce it in places, seams I have replaced with double line if stitching. It seems to hold up well now, but the two zippers doesn't zip together anymore.
After all the enforcments I have done I'm thinking it might be worth replacing the zippers. It's a light weight thing, doesn't hold much, but it's easily a bit of weight if it's filled up with a few groceries or whatever I end up bringing with me along the way. The zippers are plastic, the type you cut off by the meter and stitch one end to hold together. They worked fine when new, but they started acting up after only a couple of weeks. Are there dependable replacement zippers?