These screen clips are strong and they keep your slithering friend or four-legged scaly friend in their enclosure with no problem. It does take a little bit to figure out how to put them on, they are tricky…no lie. I bought 4 and I have a 40 gallon breeder tank for my snake and it only took two clips and I cannot budge the screen top. So now I have 2 extra which is fine, but I know I can use them too. But overall…BEST SCREEN CLIPS OUT THERE!!!