SpecSeal® Curtain Wall Mullion Plugs are precision‑engineered, fire‑retardant foam inserts designed to fit seamlessly into the voids of aluminum curtain wall framing members. Manufactured to match the exact size and shape of each mullion cavity, these resilient plugs provide an efficient, code‑compliant solution for fireblocking and smoke‑sealing within hollow aluminum framing. Constructed from durable, sound‑absorbing foam, the plugs maintain stability across a wide range of environmental temperatures, helping improve both acoustic performance and fire resilience. During fire exposure, the intumescent technology embedded within each plug expands 10–15 times its original size, forming a dense, insulating barrier that effectively impedes the spread of fire, smoke, and hot gases through the curtain wall system. Ideal for commercial, high‑rise, and unitized curtain wall construction, SpecSeal Curtain Wall Mullion Plugs deliver a fast, reliable, and time‑efficient method for enhancing perimeter fire containment.