Bostik Fireban One is a fire rated intumescent low modulus, one component, class A polyurethane, When cured it will form a tough, flexible fire rated seal capable of cyclic expansion and compression movement of 50% (+ 25%) of the original installed joint width Fireban One is resistant to normal weathering conditions such as rain, sunlight, snow sleet, ozone, atmospheric contamination and pollution. Its excellent weather ability enables it to retain its original properties after years of exposure.