Abstract: A unitized seal for use in a gas spring seal assembly. The unitized seal includes a rigid thermoplastic insert having an elastomeric sealing layer surrounding the insert and bonded to the insert. The insert provides rigidity to the seal and includes a central, axial opening that receives and guides a rod slidably engaged with the insert. The sealing layer engages the interior surface of the gas spring cylinder to prevent the pressurized gas contained within the gas spring from escaping around the seal. The sealing layer also includes a central, axial opening aligned with the passage in the insert that slidably engages the rod and further prevent gas from escaping the gas spring cylinder. The unitized seal may be formed in a single or two-step process. In the single step process, the insert and sealing layer are formed by injection molding processes in a single mold and are bonded to one another by a subsequent covulcanization process.