Marlon 25mm Heatguard Opal Multiwall Polycarbonate Roof Sheet 4000mm x 700mm x 25mmProperties High impact resistance: up to 200 times greater than glass. Excellent protection: against hailstones, vandalism and accidental damage. Insulating glazing: which can achieve a sheet uValue of 1.6 W/mK. Externally: silver grey in colour. Internally: opal surface. Creates: a soft light quality. Reduces: heat build up by up to 50% compared to clear material. Prevents: the conservatory from overheating in hot weather. Eliminates: the need for blinds. Light transmission: 7% which blends with dark coloured conservatories. Up to "Class 1" fire rating: polycarbonate is a self-extinguishing material which will melt away from the flames, stopping as soon as the source is removed. Note: 6mm Twinwall does not have a Class 1 fire rating. High strength: weight ratio. Cost effective: as sheet weight is low, support structures can be lighter providing cost effective buildings.Marlon provides high levels of insulation.