Klober Flavent uPVC Roof Breather Vent with Extendable Flange - 125mm Product features & benefits Prevents cracking of roof membrane Allows moisture to be vented from the roof Does not affect the thermal performance of the roof insulation Watertight, strong and durable Fire rating B2 Resistant to temperatures -40°/80°C (no direct flame contact) Flow temperature max. 40°C Klober's Breather Vents for flat roofs allow moisture to escape from unventilated warm roofs and can be used to ventilate a cold roof loft space.