Charleston has heavy-duty, hot-dipped galvanized steel sections with an epoxy primer and a baked-on polyester finish to resist rust and impact. A galvanized steel track and durable, steel wheel, ball bearing rollers assure long lasting performance. To protect against the elements, a bottom weatherseal provides an effective barrier along the entire length of the door. Roll formed tongue and groove meeting rails seal out wind, rain and snow. Finally, a thick core of optional polystyrene insulation helps keep your garage quieter and more comfortable.