High strength, heavy duty hexagonal construction screws with diameters from 1/2" to 1-1/2" are covered by the ASTM A325 standard. Because these bolts are intended for use in structural connections, the thread length is shorter than regular hexagonal bolts. For thread lengths and other relevant dimensions, please see the structural bolts page on our website. This specification applies only to strong hexagonal construction screws. Screws with comparable mechanical properties but different shapes and thread lengths are covered in specification Astm A449. Specification A449 covers screws for general purpose use, including anchor screws. For screws and bolts of tempered steel greater than 1-1/2 in. in diameter and with comparable mechanical properties. The F3125 specification is a consolidation and replacement of six ASTM standards, including; A325, A325M, A490, A490M, F1852, and F2280