A prosthesis is specially designed to replace a body part either missing or to make it work better device. In the case of penile prosthesis it serves to hold this body straightening and also helps them erections last longer. When other medical treatments for impotence have not proved satisfactory and comfortable, the penile prosthesis is often a good choice. There are two main groups: the flexible and inflatable. The first, of silicone or polyurethane, are introduced into number two within the corpora cavernosa of the penis, allowing an erection firm enough for penetration to occur. The size of the prosthesis fits the penis, and all parts are invisible as are inserted under the skin. Such air or hydraulic work by a similar mechanism that occurs during erection and allow natural sagging state. The choice of one type or another depending on the type of patient.