Petzl Ultralight is a very innovative crampon bag: it will look like a simple bag but instead it is made with a particular material (X-Pac) that makes it really super resistant. It is compatible with all types of crampons and is convenient for storing them in your backpack. The closure is via a simple flap or a small carabiner. You can also use it as a mat to sit on the snow without getting wet due to its complete waterproofing! Petzl Ultralight crampon bag