The panels are affordable, durable, and easy to use without instructions. They are very low profile, and help smooth out the rough areas of a KeyMod handguard.
My only (minor) complaint was that I needed an extra panel (6 rather than 5), but these are only sold in 5-packs. I found that, in my case, I need 6 panels if I want to completely fill all of the KeyMod holes on the 3, 6, and 9 o'clock sides of my 15" rail. Is it a big deal? No, it's mostly aesthetics, honestly. Also, I'm sure others found 5 to be the right amount for their needs, while some people only needed 4!
This is not a defect of the product (I knew what I was getting), so I'll give it 5-stars anyway. I guess the lesson here is to buy two packs of these and have spares!