Invisible zipper?

I kind of thought that, too. But how could they sell so many pillows for .99 if they had to buy the zipper?
Was also thinking of the envelope closing?
Also, the closure that zip lock bags have. It looks a bit like a zipper but is all plastic.

Slide fastener is the first name they had for zippers. As for selling pillows for $.99 there is something fishy there. Even a 12 inch pillow (very small) would take 1/3 of a yard of material plus whatever it's stuffed with. Even wholesale the materials would cost more than that and where is the profit.....EXTREMELY FISHY

Agree with Myrna, that is what they first called zippers.
The Hidden would be like a Lapped Zipper, conceals the zipper color and teeth, they do this on fashion pillows.
This way they can put a odd color zipper in or maybe cover some cheap metal ones.
Also agree that has to be made of some low quality materials. Just my Humble Opinions

You can always contact the seller with questions.

Fishy is right. Check the shipping charges. Unscrupulous sellers try to cheat ebay out of its portion of profits by pricing the object for sale absurdly low and charging an outrageous shipping price.