I recently bought a pair of second hand Oakley Xsquared (Carbon) and I noticed that they are a little bit lighter compared to my Oakley Juliet (Plasma). I just want to know if it's true or the weight depends on the type of frame (Carbon, Plasma, Polish, etc.). . Though the metal looks and feel sturdy, it just bother me that it's not equal to or heavier than the Juliet. Thanks!