It also provides an effective barrier against the common causes of corrosion in aircraft today. PR 1771 Class B will resist aircraft fuels (aviation gasoline or jet fuel), oils and hydraulic fluids. PR1771 Class B is a two-part manganese cured, based on Permapol P-5 liquid polymers, a chemically modified improved class of polysulfide polymers. The mixed compound is a thixotropic paste which can be readily applied by spatula or extrusion gun. It does not flow from vertical or overhead surfaces.