Pretty easy to insert, the sponge birth handle is placed in the vagina and prevents pregnancy by releasing a spermicide. It works by killing or paralyzing the sperm that comes into the vagina. A dimple on one particular side of the sponge fits more than the cervix to type a barrier to prevent sperm from reaching the egg. This dimple also lessens the chances that the sponge will move out of location in the course of sexual intercourse. My co-worker found out about Active Agent In Clotting Sponge Approved By The US Department Of Defense by browsing the Internet. Obtaining only one size, the other side of the sponge has a loop for easy removal following use.