If you have some that never grew fur, they are not true hairless hr/hr. They would be fuzzy hairless which is an entirely different gene. True hairless grows their hair fully in and around the age of 2 weeks starts to lose it around the face-- the hairless slowly progresses from the head to the shoulder, down the back and the rump is the last place to lose the hair. They are quite fascinating to observe in this silly process. haha