With middle school students I need to make every dollar I have stretch with school supplies. I use to buy Avery but the cost was getting to expense. I saw there was a sale price on these sheet protectors. I tried them out and they served there purpose. I now only purchase these sheet protectors.
I needed to create a binder with sheets of information that I will need to reference to often so I knew the best way to protect them from getting folded/worn/etc was to buy clear sheet protectors. These worked just fine. They aren't the thickest which for my situation was just perfect. I wouldn't use them if you wanted to present a portfolio formally but for everyday use they are prefectly fine.
Our previous extra capacity C-LINE top loading sheet protectors maxed out at 25 sheets. Even the ones at another office supplier hold only 50 sheets. At 70 sheets this beats them all; although we're not likely to put that many in. Even with 25 one should use a 1/4" binder clip to make sure that they don't all scatter if they slip out and fall to the floor.