Rationale: AMS3278B results from a Five Year Review and update of the Types of this specification. Revised Classification Types to distinguish non-corrosion inhibiting from corrosion inhibiting materials. Eliminated Class B-1/4 solvent free sealing compound and all related requirements. Removed Air Content requirement. Increased 14 day hardness to 50 Shore A. Removed Class B for Shear Strength Table 1. Revised Viscosity of Base requirement for Class A and Class B. Lowered the maximum viscosity for Class A Application Time.