RX6448 takes a 140mm metal temple arm on an irregular, not-quite-round-not-quite-square front — a shape that makes the hinge position more specific to this model than it would be on a plainer round or square frame. This aftermarket pair is cut to that 140mm metal spec accordingly. Cross-checking the model number against the arm being replaced is more reliable than matching by shape alone, given how many Ray-Ban models share a broadly similar irregular outline.

Irregular fronts like this one don't change how the arm itself ages — it's still the hinge screw and the tip sleeve that wear first, same as on a round or square metal frame. What the irregular shape does affect is fit: because the hinge sits at a shape-specific angle, it's worth checking the model number carefully rather than assuming any 140mm metal Ray-Ban arm will seat the same way.