The firesleeve material is elastic and easily slides over the fittings, including 90 degree elbows. Once the firesleeve is installed, the heat shrink tape seals the ends of the firesleeve.  The firesleeve product is made of knitted braided fiberglass yarns on a flexible substrate which is coated with a high grade silicone rubber.  They protect continously to 500 degrees F and will withstand a molten splash at 2200 degrees F.