Rapid Cure Integral Fuel Tank Sealant | 6oz, 2hr, NSL1422RC, Class BNSL1422RC Class B is a fuel resistant sealant for use on integral fuel tanks and pressurized cabins as well as other areas subject to contact with aircraft fuels, lubricants, oils, water and or weathering. This Class B two part polysulfide base compound cures at room temperature to a flexible, resilient rubber. Model (EDMO# 1422B26) is Class B, 6 ounce size with a 2 hour work time.