This article is from the Impotence FAQ, by Sine Nomine firstname.lastname@example.org with numerous contributions by others.
There are three sorts of implants: semi-rigid rods, multi-component
inflatables, and self-contained inflatables. The simplest of these,
semi-rigid rods, consists of a pair of flexible rods that are
implanted in the penis. The penis is always erect; most of the time it
is bent down, but when intercourse is desired it is straightened
out. It can be hard to hide the always-erect penis under clothing.
Multi-component and self-contained inflatables both have three parts:
inflatable cylinders, fluid reservoir, and pump. In multi-component
implants, the pump goes in the scrotum, the cylinders go in the penis,
and the reservoir is in either the abdomen or the scrotum. To have an
erection, you squeeze the pump in your scrotum until the cylinders
fill; to end the erection, you squeeze a release valve. Self-contained
inflatables have all the parts in one unit; erection is achieved by
squeezing the head of the penis and released by bending the penis.
Implant surgery is not reversible and should be considered only as a