Expanded Polyethylene (EPE or EP) wads serve entirely different operational functions than induction liners; they act as non-induction, pressure-sensitive, or purely mechanical fluid-tight gasketing liners. Manufactured through the highly controlled extrusion of low-density polyethylene (LDPE) injected with a physical blowing agent, EPE forms a robust closed-cell matrix. The industry standard architecture for high-performance EPE wads, such as the Tri-Seal F-217, is a sophisticated co-extruded three-layer system: a central core of expanded polyethylene foam flanked by two outer layers of solid, unfoamed polyethylene film.