The KoldLok Round 4" Grommet is the premium choice for your facility. Its revolutionary sealing technology greatly reduces costly bypass airflow, increasing useable cooling unit capacity, and ensuring maximized efficiency from HVAC equipment. The KoldLok Round 4" is designed to seal openings in new and existing raised floor cutouts to block bypass airflow and maximize cooling system efficiency. New Hybrid Brush Technology (HBT) is uniquely constructed to offer a flexible and highly efficient sealing membrane and multi-layered construction for increased sealing effectiveness.