Primo Grills Cast Iron Lump GratesCast Iron Replacement Charcoal Lump Grates Upgrade or replace your worn Primo lump grate with a heavy duty cast iron original. These grates sit near the bottom of the firebox and support your lump charcoal while maintaining strong airflow through the cooker the key to clean, consistent burns. Lump Grate Highlights Heavy duty cast iron: Built to withstand extreme heat and heavy charcoal loads. Better airflow, better fire: Holes allow oxygen to move up