The “144” in TNA® 144 is the minimum tensile strength of the bolts; 144ksi. A325 is 120ksi and A490 is 150ksi. Our 144 ksi tensile strength allows us to use A325 raw material but achieve A490 tension values. We get all the benefits of A325 like ductility, coating options, and low cost while gaining the value of a higher strength fastener that will allow for fewer bolts in a connection.