RB3689 Aviator Metal II takes the same 140mm metal arm length as the base RB3025 Aviator, with 'II' marking an updated bridge and front design rather than a different temple. This aftermarket pair is cut to that shared 140mm aviator spec. Matching that figure matters more than matching the roman numeral in the name, since 3025 and 3689 arms are functionally the same part.

As with most thin-gauge aviator arms, the parts most likely to need attention are the hinge screw, which loosens with repeated folding, and the tip sleeve near the ear, which hardens and can crack well before the metal arm itself shows any real wear. It's worth checking both before assuming the whole arm needs replacing — sometimes it's just the sleeve, though a bent or cracked arm calls for the full swap. Either way, the fix stays limited to the temple, not the front.