... any angle freely 3,Slat width:16mm,25mm Hollow shutter 1. Sound insulation---its special structure ... ’t produce any pollution. In addition, the hollow glass are sealed, so the sheets are not ... 4. Energy-saving---Because the thermal transmittance of hollow glass is lower than single glass, the K ... of energy sources.5. Safety—Due to the hollow glass shutter using double- toughened glass, its weatherproof ...