emko door sweeps are designed to seal the gap between the bottom of the door and the top of the threshold as well as keep it free from any small dust or debris. Tightly knit 5/8" nylon fibers work just like a broom, clearing the doorway with each open and close of the door. All brush seals greatly reduce the infiltration of light, air, wind, rain, and snow; prevent heat loss; control the penetration of smoke and fumes. The brush remains flexible down to -40 deg F and has a melting point above 400 deg F. That means that any normal condition that the brush is exposed to will not affect the integrity of the brush. Aluminum finish includes gray nylon brush, others are black.