Mentor Siltex vs smooth round?

Thank you for your question.  Generally speaking in my experience because of the Siltex textured implants have a thicker wall, textured implants can to feel a little firmer than a smooth breast implants.  The size differences that you mentioned are minimal and are related to the texturing on the Siltex.For more information please read the following link:

as some things don't make sense when viewing catalog dimensions. Regardless, as far as I know, the filler silicone is the same in both styles of implants.  I haven't figured out why some surgeons like round textured devices over the more commonly used smooth round implant.

The difference in measurements are quite small.  2 millimeters differences in width and projection will be virtually undetectable after the implants are put in.  The more important question is why we use textured or smooth implants for each patient.  In my practice I usually use textured for above muscle placement and smooth for under the muscle.