2 yards (90): recommendations of 1~2 years old， 15~22 kg

3 yards (100): recommendations of 2~3 years old， 22-28 kg

4 yards (110): it is recommended that the 3~4 years old， 30~35 kg

5 yards (120): it is recommended that the 4~5 years old， 35-40 kg

6 yards (130): it is recommended that the 5~7 years old， 40-55 kg