STI's 4 in. SpecSeal® Cast-In Device Extension Kit provides a practical way to extend a 4 in. Cast-In Firestop Device as concrete slab depth increases. The SpecSeal Cast-In system combines a sleeve, concrete form, and intumescent firestop into an integrated penetration solution, while the extension allows the assembly to accommodate greater pour depths. The extension is compatible with tested firestop assemblies rated up to three hours when installed as specified. STI identifies the Cast-In system as water resistant and smoke sealing, with testing to ASTM E814 (UL 1479) and CAN/ULC-S115, while the 4 in. device family is FM Approved.