Saline implants can be inflated to the desired size with sterile saline. They are inserted during surgery completely empty, and the surgeon fills them with saline solution during surgery. Since the implants are empty when they are surgically inserted,the scar is slightly smaller than is necessary for silicone gel breast implants (which are filled with silicone before the surgery is performed). All implants, including saline implants, vary in shape, volume, expandability, shell thickness and shell surface. Therefore, they are easy to customize to your overall body height, weight, chest length, chest width, and current amount of breast tissue..  

Saline implants have a silicone rubber shell that is inflated to the desired size with sterile saline. Most implants have a valve that is sealable by the surgeon.
There are two types of saline-filled implants. One type is a fixed volume implant, which is filled with the entire volume of saline at implantation. Another type is an adjustable volume implant, which is filled intraoperatively and has the potential for further postoperative adjustment.
FDA Approval
On May 10, 2000, the FDA granted approval of saline-filled breast implants manufactured by
Mentor Corporation and McGhan Medical.