The price I thought, $15 for 3, was a bit high but the product fits on both a Macbook Pro and Air, and seems to “work fine.”
I’m pretty sure, and read as much, that these won’t work that well on a mobile phone or other device which has more in-and-out-of-pocket type action. They are attached by adhesive, so that would probably wear out. But for laptop use they seem great.
I had been covering my webcam for years with black electrical tape, but that is less than ideal if you’re regularly engaging in video conferencing, and having to remove and reapply the tape with any regularity. This is nice because it operates by a simple slider mechanism, and I like the peace of mind it offers by being able to instantly visually verify that your camera is closed.