SpecSeal FP Intumescent Firestop Plugs are easy to install, creating a robust seal against fire and smoke. Firestop Plugs make an excellent solution for temporary installation overnight as well as permanent long-term seals for blank openings and cable penetrations. Sized to fit 2″ and 4″ diam. openings, firestop plugs make sealing conduit stubs and sleeves a breeze.