Because all the layers are sewn together, absorbency cannot be customized, but AIOs are available in many different specialized absorbencies. They consist of a core of absorbent fabric between a top and bottom layer. They usually have wings to fasten around underwear with snaps or hook & loop. They are often backed in a waterproof or water-resistant material.
AIO pads with no waterproof or water resistant layer are known as a "non-waterproofed AIO".