The three types of silicone gel-filled breast implants are as follows:

• One type is a single lumen implant that is prefilled by the manufacturer with a fixed volume of silicone gel.

• A second type is a double lumen implant with (1) an inner lumen prefilled by the manufacturer with a fixed volume of silicone gel and (2) an outer lumen that is filled during the operation with a fixed volume of saline through a valve.

• A third type is a double lumen implant with (1) an outer lumen prefilled by the manufacturer with a fixed volume of silicone gel and (2) an inner lumen that is filled during the operation with saline through a valve. This type of implant allows for adjustments of the saline volume after the operation.

A silicone gel-filled breast implant has a silicone rubber shell with the same general composition as shown in the <A href="http://www.fda.gov/cdrh/breastimplants/handbook2004/devic