When sourcing firestop products, you must prioritize material composition and application suitability. Key specifications include the Fire Resistance Rating (FRR), typically ranging from 1 to 4 hours, and the Expansion Ratio for intumescent materials, which should be sufficient to seal gaps as substrates melt. Ensure the product is compatible with the specific penetrants, such as PVC pipes, steel cables, or HVAC ducts, and verify the smoke leakage rating (L-rating) to prevent toxic gas migration.