ASTM F959, Type A325 DuraSquirt® Direct Tension Indicator (DTI) washers are used to indicate the correct bolt tension when an A325 structural bolt is installed. The DuraSquirt® 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. DuraSquirt® washers provide all the same advantages as the standard Squirter washer, but have the added benefit of the silicone used being designed to withstand exposure to the elements. Dimensional specifications are governed by ASME B18.2.6. Available in mechanical galvanized finish, which provides a corrosion resistant zinc coating.