I too have always heard a horses legs are close to the size they will be... That is why people make a big deal out of long legged foals...
I don't under stand kg... cm... or mm in horses. XD I do pounds and hands high... I had a foal that was pretty small born here.. let me get a picture.
He was extremely small, could it under momma easily. When he was a yearling, he ws probably about the size of this years colt who is only five months old right now. l.jpg
Compared to this year's foal, who tried to go under momma and would send her up on the tip of her hooves. 430388_360611293969461_270752023_n.jpg
(Excuse the horrible picture.)