Go and get a chip clip out of your drawer. Any of them. Count the parts.
You will find two or three pieces, and if you then ask which of those pieces fails, the answer is almost always the ones that move. That is the whole observation this product came out of, and it is not a clever one. It is just one that nobody selling two dollar chip clips has any reason to act on.
A SLIDESEAL is one piece with two magnets sealed inside it. Here is what is missing and what each missing thing was costing you.
No spring
A spring is a part whose entire job is to be under load constantly. That is also the condition under which materials fatigue. A steel spring in a kitchen drawer takes on moisture, oil and salt, and a plastic one creeps, which means it slowly relaxes toward whatever shape you have been holding it in.
You have felt this. A clip that gripped when it was new and now sits on the bag without really holding it has not broken. It has relaxed. There is nothing to fix because nothing is damaged. It simply is not a spring any more.
If the grip does not come from stored tension, there is no tension to lose.
No hinge
Most plastic clips use a living hinge, which is a thin strip of the same material, bent repeatedly. These are genuinely clever and they are cheap, and polypropylene tolerates a remarkable number of cycles when the hinge is designed well and the part is moulded well.
The trouble is that the hinge is also the thinnest section of the part, so it is the coldest spot in the mould, and it is where stress concentrates. Flex it enough times, especially cold, and it whitens, then it splits. Once it splits there is no repair available to anybody.
A clip with no hinge has no thinnest section waiting to go.
No clasp
A clasp is two surfaces that have to stay the exact right distance apart forever. They get worn by use and fouled by whatever is in the drawer, and the tolerance that made the click feel satisfying in the shop is the same tolerance that makes it stop catching a year later.
Nothing to click shut means nothing to click open on its own at the back of a cupboard.
So what is left
A single piece of plastic with a slit cut through it, and two magnets sealed inside the body so there is no glued-on magnet to come unglued.
You fold the bag, you slide it on, and the two faces of the slit hold the fold under pressure for six continuous inches. The grip comes from the geometry of the slit and the stiffness of the material, which do not get tired, because neither of them is doing anything. Nothing on it moves, so there is nothing on it to break.
The shape is the subject of a pending design patent application. The reasoning above is not proprietary and never was. It is sitting in your junk drawer in three pieces.
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