Your looking at about a 8-10in on average. Some may get bigger while some may stay smaller but generally they tend to cap out at the 8-10in mark like most other FH's. Males tend to only be a couple inches longer on average compaired to females so there honestly isn't much of a size difference between males and females fully grown, well other then males tending to be a bit thicker then females. Also it generally takes about 2.5-3 years for em to max out in size.