145mm is the one number that has to match on a Ray-Ban RB3647N temple arm, and it's what this aftermarket pair is cut to. Beyond length, fit depends on the hinge cut lining up with the RB3647N mold, which is specific to this model rather than shared across the wider RB3600 range. Confirming the model number on the arm you're replacing, rather than judging by eye, is the safest way to be sure a replacement will seat correctly.

On most Ray-Ban frames, a temple arm is the single point most likely to fail before the front does — a bent hinge, a snapped tip, or a stripped screw hole, while the lenses and front frame are still in good shape. Replacing the arm alone, rather than the whole pair, is the cheaper route whenever the damage is limited to one or both temples. It also makes more sense than retiring a sound front frame over a single broken part.