The ThermoBall eco Triclimate Jacket delivers the original mountain layering system concept in a modern form. Two jackets, which can be worn alone or together, see you well equipped for variable conditions on the hill.Made from a waterproof stretch DryVent, the outer is comfortable and protective. The removable inner is filled with ThermoBall eco synthetic insulation. Light, warm, and compressible, it will continue to insulate even when wet. Practical and adaptable, in the depths of winter wear zipped together for maximum hiking performance.