ASTM F959, Type A325 Squirter® Direct Tension Indicator (DTI) washers are used to indicate the correct bolt tension when an A325 structural bolt is installed. The Squirter® DTI is placed under a hardened surface such as a bolt head, nut, or hardened washer, with the bumps facing away from the structural steel. As the bolt is tensioned, the clamping force flattens the bumps, reducing the gap which causes a colored silicone material to squirt out, giving the visual indication that the bolt has reached its proper tension. Dimensional specifications are governed by ASME B18.2.6. Available in mechanical galvanized finish, which provides a corrosion resistant zinc coating.