Standard Document L door: 4 mm Planitherm Total + Toughened internal glass, 12 mm airspace, argon gas, 6.4 mm laminated external glass., Heritage Double glazed door: 4 mm Planitherm Total + Toughened, 4 mm airspace, argon gas, 6.4 mm laminated external glass., Heritage Double glazed door: 4 mm Planitherm Total + Toughened, 6 mm airspace, argon gas, 6.4 mm laminated external glass., Heritage Double glazed door: 4 mm Planitherm Total + Toughened, 8 mm airspace, argon gas, 6.4 mm laminated external glass.