Standard Features include Seismic and wind restraint consistent with current building codes. (Note: Equipment geometry, attachment, and anchorage may affect restraint capacity) Access ports for each isolator to inspect, level, or change springs after equipment placement Up to 4 inches (102 mm) deflection, powder-coated steel springs with 50% overload capacity High-frequency noise isolation pads Environmentally inert elastomeric seal for an air and water-tight closure between the curb and isolation rail Supply and return duct support hardware Structural steel curb with wood nailer 21-inch Standard Curb Height.