Girth expanding penile prosthesis cylinder

An implantable penile prosthesis comprising:

• a pair of inflatable penile prosthesis cylinders, each penile prosthesis cylinder having a longitudinal axis and comprising an inflatable portion including a chamber wall defining an inflatable chamber, the chamber wall comprising at least one thin wall section and at least one thick wall section;
• a reservoir containing fluid;
• and
• an inflation apparatus configured to transfer fluid from the reservoir into the inflatable chamber to transition the inflatable portion to an inflated state;
• wherein the at least one thin wall section stretches a greater amount than the at least one thick wall section in a plane extending perpendicular to the longitudinal axis when the inflatable chamber is transitioned from a deflated state to the inflated state.