When the new class U20 was formed, a different specification from that of IAAF was in force in some countries and at some competitions. At first, according to the rules of IAAF, the height of the hurdles for juniors was 107cm, but in some countries a-metre-high hurdles were still used. What is more, sometimes a shot of 6.25kg was used instead of a 6kg one. All in all, it’s quite confusing. Does anyone have more information on the matter?