Bonded seals are metal washers with rubber inserts for use in high-pressure applications. The washer resists the bursting forces and limits the deformation of insert, which is self-centralizing and bonded to the washer's inside diameter. Most bonded seals consist of a rectangular washer and a trapezoidal rubber insert. The insert is vulcanized to improve material properties such as hardness, strength, and elasticity. As captive assemblies, bonded seals can be used in applications with thread undercuts. Bonded seals use many different types of metal washers. Material of construction include aluminum, brass, bronze, copper, mild steel, and stainless steel.