I.ve had a look in one of my ferret books it said the size varies with the sex to sart with, and the average weight must be taken when the animal is reasonably well-fed. A fit (not fat) hob ferret averages around 2 1%2 - 3lb, with the jill averaging 1 - 1%2lb. The overall lenght is something in the order of 20in for the hob and 12 - 15in for the gill