An adjustable implant for volumetrically altering, replacing, expanding, or augmenting tissues is provided. The implant includes an elastomeric membrane enclosed or partially enclosed about a main chamber. The implant is adapted to expand when filled with a fluid. The membrane includes an outer zone formed from at least one outer elastomeric layer； an inner zone formed from at least one inner elastomeric layer； and a middle zone formed from at least one elastomeric middle layer positioned between a least a portion of the outer zone and at least a portion of the inner zone. The implant is configured such that the middle zone is under contraction from a contracting force provided by the outer zone or the inner zone. A method of forming a fluid-filled adjustable implant for volumetrically altering, replacing, expanding, or augmenting tissues is also provided herein.
