These durable cases protect your memory cards from getting wet, contaminated with dirt, or in my case lost. I have misplaced numerous memory cards due to their small size. With these cases not only do I not lose the cards, but I use the cases to organize them. The cases are small and compact (about 4.25" x 2.25") and only about 1" thick. They're available for almost all media types: SD/Mini SD, XD, Compact Flash and for MS (Memory Stick) cards. Each holds anywhere from 4 to 16 memory cards. I now use them to organize all of my media. So my wife has hers (I am not allowed to touch them since I have lost some of her photo flash cards), some for work (sorted by major projects) and then my own personal use cards. All I have to do now is grab the case I need for work, for instance, and I know I will have everything I need. These card cases have an o-ring seal Pelican says is "water-resistant." Though I wouldn't want to find out if they're waterproof, I think they only back off that claim to protect their tail. I have owned Pelican cases for my cameras for years and have found they're pretty much bulletproof. I also have one case for my laptop and use Pelican's cases for work to ship expensive equipment. My only complaint with their card cases is I wish that they had different colors to chose from so I wouldn't have to label them.