In August of 2007, A307 Grade C was officially replaced by the new F1554 Grade 36. Although these two grades are nearly identical, there are some subtle and important differences. These specifications cover anchor bolts to be embedded into concrete. Unlike the A307 Grade C specification, F1554 also allows for headed anchor bolts, whereas A307 Grade C only covered unheaded anchor bolts that were bent or straight. It is preferable to use F1554 Grade 36 instead of A307 Grade C for anchoring purposes. However, Portland Bolt can still manufacture A307 Grade C anchor bolts if a project requires them.